DESCRIPTION OF A VEGETABLE AND ITS PARTS.
As has been said before, it is extremely difficult to make any distinction between the lower tribes of the vegetable and animal kingdoms, and physiologists are not yet agreed, with respect to some members, as to which kingdom they belong. Their whole substance is made up of cellular tissue, and there are but few distinctions of parts, forming generally a broad foliaceous expansion called the "thallus," as in lichens and sea-weeds, or a sort of root composed of fibres and called the "mycelium," as in the fungi. But, a very few steps higher, the distinctive characters become so evident that they are impossible to be mistaken, the following description will therefore apply to vegetables of the more elevated character, such as trees or flowering plants.
Plants are fixed to the earth, and receive nourishment from it by imbibing its liquids, which circulating upwards through the porous structure of the plant itself, and becoming exposed to the air in the leaves, attract to themselves nourishment from that source also. The part of a plant which grows into the earth is called the root; this has a variety of forms, in some it is branched like the upper part, and these branches divide into rootlets or fibres penetrating deep into the ground, and absorbing nourishment in all directions, but this absorption does not take place from the whole surface of the root but from spots covering it, and from the slightly expanded ends of the fibres, these portions are formed of new and porous cellular tissue, and are called "spongioles." The part of plants which springs upwards from the earth is called the stem, if large the trunk, this divides into branches and twigs; stems in some cases continue for a distance more or less underground. The part of a potato plant, usually called the root, and from which the tubers or potatoes grow, is in reality an underground stem, and the fibres which spring from it are the roots; the underground suckers of mint are also portions of stem, and in some cases these are greatly expanded, they then obtain the names of "tubers" (as the potato), or "corm," as in the crocus and meadow saffron; when the stem is thin and runs along the ground, sending in roots at intervals (as in the strawberry), it is called a "runner," when thicker and running horizontally under the ground, it is called a "rhizome."
The stem consists of a central portion, either made up of long bundles of woody fibre running side by side, as in the endogenæ, or deposited in rings and having a central cylinder of pith, as in the exogenæ. In these the wood at the central part (or the oldest) is called "duramen," or "heart-wood," while that at the outer part or nearest to the bark (the newest), is called "alburnum" or "sap-wood." The former is the harder and the latter the softer portion. From the pith in the centre, through the woody part, rays or laminæ of cellular tissue similar to that which constitutes the pith itself, are sent outwards through the woody rings to the inner part of the bark, which they form; these are called medullary rays, and may be seen in wood which has been cut across the grain, they are often called the "silver grain," and are very evident in oak, beech, and elm, the inner part of the bark is called the "liber." The bark itself is made of cellular tissue dried and hardened by age; the outer portion (called the "epidermis") is in many cases shed, and may be constantly seen hanging loosely from the bark of the birch and other trees in loose white silvery portions. The outer part of the bark of some trees is so largely developed as to be of considerable thickness, this is especially the case in the Cork oak (Quercus suber), which is the cork of commerce. The bark cannot stretch as the circumference of the tree increases, it is therefore split up and cracked, which accounts for the rough state of it on those trees which do not shed the outer part.
The chief appendage of the branches, is called a leaf, it grows from a small projection called a leaf-bud, which contains the leaf rolled up. The method in which this occurs is different in different plants, in some it is folded backwards and forwards, in others doubled up with the opposite leaf alternately, and in various forms in other plants. The leaf consists of two parts, the stalk (petiole) and the blade (lamina); the blade is of different forms, and has ribs and veins covering it, in some of a reticulated or network pattern, these belong to the exogenæ, and in others running parallel, which is the kind of venation found in the leaves of the endogenæ. When leaves are placed on a stalk, they are said to be "petiolate," when without one, "sessile."
When leaves are not separated into different portions (although they may be much notched) they are said to be "simple," as in the oak or willow, but when divided into separate portions, as in the ash, they are said to be "compound."
The following are the chief forms of leaves, named according to variations of their several parts:
DEPENDING ON FORM.
DEPENDING ON MARGIN AND ARRANGEMENT.
DEPENDING ON POINT.
At the base of many leaves are a pair of scales called stipules; the petiole or leaf-stalk is generally cylindrical, but frequently triangular, and in grasses it is flat and surrounds the stem, this is called a sheath; when leaves are narrow and not expanded into a lamina, as in the pine tribe, they are said to be "acicular."
The stalks which bear the flowers are called "pedicels," at the base of which are a pair of scales called "bracts;" when these are large and expanded, so as to enclose the flowers, they are called "spathes" (this is seen in the arum), and when there are a number of flower-stalks arising from one point the bracts there collected are called an "involucre." A flower consists of several parts, the outermost green scales, composing a set, are called the calyx, and each part of it, is called a "sepal," within this is the "corolla" or that coloured part which forms the most characteristic feature of the flower, each part of the corolla is called a "petal;" when the corolla consists of but one piece, it is called "monopetalous," and when of many, "polypetalous."
The forms of corolla vary according to the form and the mode in which the petals are placed, whether united or separated, and to what extent, whether regular or irregular; the most usual forms are the following:—
Campanulate
(Bell-shaped), Canterbury Bell.
Rotate (Wheel-shaped),
Woody Nightshade.
Hypocrateriform
(Salver-shaped), Phlox.
Infundibuliform
(Funnel-shaped), Tobacco.
Labiate
(Having Lips), Bugle.
Ringent
(Grinning), Sage.
Galeate (Helmet-
shaped), Monk's-hood.
Pappilonaceous (Like a
Butterfly), Sweet Pea.
Cruciate (Like a Cross),
Cuckoo-flower.
Within the corolla are placed the "stamens" (male reproductive organs) these consist generally of two parts, the head and stalk, the former called the "anther" and the latter the "filament," which last is sometimes absent, and the anther is said to be "sessile;" on the surface of the anther is the "pollen" or fertilising dust.
Within the centre of the flower is the "pistil" (female reproductive organ), this consists of one or several cells called "ovaries," from the pistil a tube rises, having an expanded end called the "stigma," it is by the application of the pollen dust to this stigma that the ovaries are fertilised, and the various insects, especially bees, who seek for honey, shake off by their movements the pollen from the anthers and cause it to be applied to the stigma, thus unconsciously performing a necessary office for the plant while they rob it of that only which is not required.
The stamens are sometimes separate, sometimes bound up into one or more bundles, and are placed in various situations, names are given to describe such arrangements as follows:—
Stamens in one bundle, Monadelphous.
Stamens in two bundles, Diadelphous.
Stamens in more than two bundles, Polyadelphous.
Filaments placed directly below the pistil, Hypogynous.
Placed upon the sides of the calyx, Perigynous.
On the sides of the corolla, Epipetalous.
On the top of the ovary, Epigynous.
When the ovaries are fertilised the flower dies and they begin to enlarge and ripen to form the fruit, which is the pistil enlarged, and contains the ovules ripened into seeds.
The fruits of different plants are known by various names according to the state of development of the various parts composing them. If the ripe fruit split open so as to let out the seeds (as in the common pea) it is called "dehiscent," if it do not so split (as in the apple) it is said to be "indehiscent;" the outer part of fruit is called the "pericarp," and this may be soft and fleshy as in the apple or cherry, or hard as in the filbert. The following are the names of the principal varieties of fruit:—
The seed is the ovule ripened, it contains the germ of the future plant, called the "embryo," the outer part of the seed is called the "testa," and the space between this and the embryo is generally filled with starchy matter called the "albumen." The embryo consists of the plumule or stem, the "radicle" or root, and the cotyledons or leaves of the future plant; when the seed has but one cotyledon it is called "monocotyledonous" and when it has two "dicotyledonous."
Flowers are arranged in various ways upon the plants which produce them, and receive names accordingly; the whole arrangement of flowers is called the "inflorescence."
The following are the principal forms of inflorescence:—
The vegetable kingdom is divided into three great natural families, the Acrogenæ, the Endogenæ, and the Exogenæ.
The acrogenous plants are those which as a general rule have neither branches, leaves, nor flowers; they are almost wholly made up of cellular tissue, and are many of them so minute that they are quite invisible individually to the unassisted eye, and are among the most wonderful works of the Creator, having an amount of beauty in form and elaboration of ornament bestowed on them, quite equal to anything among the higher and larger creations, and yet some of these are so small that tens of millions may be placed in the space of a cubic inch, of such are the Diatomaceæ and Desmidiaceæ.
The acrogens take an immense range in the scale of organisation, from the ferns (which appear but little inferior to the exogenæ or endogenæ, have stems and leaves, and in some cases, as in hot and moist climates, assume the size and form of a tree), to the very lowest state of vegetable existence, consisting of simple cells uniting into strings or forming simple threads, such as the green algæ which form on stagnant waters and damp ground or wood-work, and the mould or mildew which forms on all decomposing substances. The general name for these acrogens, "cryptogamia," which has been in use for a long time and is commonly still used, indicates that the reproductive organs are invisible, hence the expression used by one of Shakespeare's characters, "We have the secret of fern seed, we walk invisible;" but this is not really the case, for the "sorri" at the back of fern-leaves, are vessels filled with spore cases each having a number of angular seeds within it; the lower tribes of the acrogens do not commonly grow from seed but by an extension of their several parts by the development of the cells of which they are composed, and by their separation into portions.
Few of this tribe have anything like true woody texture, except their highest order, the ferns, which form some of the most beautiful objects in the vegetable world. Few of the family of acrogens are of much direct use to man, the mushroom tribes are very generally eaten where they abound, the lichens of the arctic regions form the food of the reindeer (the greatest friend of man in these cold climes) as well as, in part, the food of man himself; but although these lowly plants serve man but little, directly, there is not a shadow of doubt that they have as important an office to fulfil as any other family or tribe of organised creatures, whose purpose may meet the eye more plainly. For all the members of creation form, as it were, the links of one great chain, and were but one removed, though it might perchance be only some poor weed or lowly moss, yet might it cause the whole to be annihilated; for certain earthy matters enter into the structure of all plants, and it appears to be the wonderful office of some of these lowest tribes of plants to prepare this earthy matter for its reception into the systems of higher organisms, for as silica is one of the primitive rocks of the earth and is only found in fragments, from the largest to the sand on the sea-shore, which is nothing but a collection of minute fragments of quartz worn small by attrition, yet a grain of sand is a gigantic mass of rock in comparison with the thin porous hollow shells of the Diatomaceæ, &c., and by far too large to be absorbed or dissolved so as to be taken into the systems of other plants that may require it, which plants would cease to exist if this earth were not thus prepared for them; now these are the corn-bearing plants, the most useful to the animal world, and upon which it in reality depends for existence. Moreover the whole of the mould in which the higher orders of plants grow, is formed by the decomposition of the more humble grades, especially the lichens, which first take possession of the surface of bare rocks and stones, and furnish by their death food fit for the sustenance of those which follow them. Like the higher orders of vegetation, these minute plants excrete oxygen, and thus in the ocean may supply this vital element for the respiration of the various corresponding minute animal organisms which inhabit the depths of the sea and which cannot come to the surface to get it, so that the two thus supporting each other, form food for all the higher marine animals, which are finally eaten by man. So that upon some of these minute and apparently useless creatures hang the lives and well-being of many of the most important vegetables and animals.
Dr. Lindley divides the acrogens into the following orders:—
1. Algæ (Algals), including Sea-weeds, &c.
The Algæ include the lowest of all the vegetative organisms, the "Protophytes" (first plants). These have no individual parts, but consist of living cells, propagating by sub-division or by the union of two cells into one, causing the formation of "nuclei" or smaller cells within them, each of which becomes a parent cell after the rupture of the cell-membrane which contained them.
Dr. Carpenter, in his "History of the Microscope," says:—"The life-history of one of these uni-cellular plants in its most simple form, can scarcely be better exemplified than in the Palmoglœa macrococca, one of those humble forms of vegetation which spreads itself as a green slime over damp stones, walls, &c. When this slime is examined with the microscope, it is found to consist of a multitude of green cells, each surrounded by a gelatinous envelope; the cell, which does not seem to have any distinct membranous wall, is filled with granular particles of a green colour, and a 'nucleus' may sometimes be distinguished through the midst of these. When treated with tincture of iodine, however, the green contents of the cell are turned to a brownish hue, and a dark-brown nucleus is distinctly shown. Other cells are seen, which are considerably elongated, some of them beginning to present a sort of hour-glass contraction across the middle; in these is commencing that curious multiplication by duplicative subdivision which is the mode in which increase nearly always takes place throughout the vegetable kingdom."
Fucus Vesiculosus.
The higher tribes of Algæ embrace the sea-weeds; these are for the most part broad, leaf-like expansions of "thallus," composed of cellular tissue, they sometimes grow to an enormous length. Humboldt mentions the sea-grass as extending for miles, and forming continuous extensions of two or three hundred feet, and the Macrocystis pyrifera attains to the length of more than a thousand. The common Bladder-wrack (Fucus vesiculosus) was formerly much used to procure soda from, its ashes containing a considerable quantity, it is also used for manure; the Laminaria digitata is eaten under the name of "tangle," and a nutritious jelly is made from the "Carigeen moss" (Chondrus crispus).
2. Characeæ (Charas). | |
Charas. | These are a kind of fresh-water Algæ, composed of tubes of cellulartissue; they are peculiar, from the fact that the spores of the planthave cilia, giving to them the powers of motion and enabling them toswim away and spread the plant afar off. It is in the Charas that thepeculiar circulation of the granules of "endochrome" called "cyclosis"is best seen. |
3. Fungi (Fungals), including Mushrooms, &c.
Eatable Mushroom (Agaricus campestris).
The Fungi comprise a great variety of vegetable growths, from the mould which grows on any animal or vegetable substance, to the mushroom. Some of the moulds or mildews found on various decaying substances are peculiar to them, and in many cases exceedingly destructive. The microscopic fungus Puccinea graminis, is the parasite which fixes itself to corn and produces the disease known as mildew, and the Uredo segetum (another microscopic fungus) causes the "smut;" the "bunt" is caused by the Uredo fœtida, and the "spur," or "ergot," which attacks rye, is caused by the Acinula clavis. These fungi completely destroy the grain of corn, in which they form, and propagate in the most rapid manner; the ergot is moreover a dangerous poison to those who eat the bread made of rye infected by it. The Truffle (Tuber cibarium) is a kind of underground fungus, and is esteemed a dainty. Mushrooms are also fungi, and several species are sufficiently wholesome; these are the Field Mushroom (Agaricus campestris) and the Fairy-ring Mushroom (Agaricus pratensis).
4. Lichenes (Lichens),
Lichen.
Are those dry scaly growths forming grey, green, or yellow spots on the barks of trees and in various other places, and they grow in a sort of leaf or scale called a "thallus." They are used as articles of food and as "dye-stuffs;" the Cetraria Icelandica is the "Iceland Moss" used here for making a sort of nutritious drink or jelly, the natives of Iceland, however, use it as common food; the Cladonia rangifarina, or Reindeer Moss, is the chief food of that useful creature which forms the whole property of the Laplander; and the Roccella tinctoria is the substance from which the dye called "archil" is procured.
5. Filices (Ferns).
Fern.
The Ferns are a very numerous order of acrogenous plants, growing in the temperate regions from a rhizome or underground stalk (commonly called its root), which throws up "fronds" or leaves with a strong midrib; this midrib is commonly called its stalk, but in tropical countries the fern stalk rises above ground to the height of 30 or 40 feet, and then it is seen that the ordinary stalks are but the midribs of the fronds. There are between two and three thousand species of fern. The fronds open in a peculiar manner, unwinding as it were from a round ball. The "sorri" or seed-cases are situated at the back of the fronds in little brown spots, each of which is found to consist of a heap or collection of round capsules, and if these be placed under the microscope they have the appearance of little membraneous cases covered with net-like markings, and at the upper part a striated band of a brown colour, which after a time stretches out into a nearly straight line, tearing open the bag or capsule, and a number of seeds escape. Ferns grow best in damp and shady situations, and will thrive well in damp mould under a glass case.
The second division of the vegetable kingdom are the Endogenæ, which are those plants growing from a central bud only, as the palms, bamboos, and canes of all kinds, the grasses and all graminiferous or grain-bearing plants, as wheat, barley, &c. They have but one cotyledon in the seed and have no bark, but in place thereof a kind of natural varnish or thin coating of silica; this varnish or external polish is seen in the stalks of corn and on canes. Their leaves are often of great size, the veins run parallel to each other (fig. 8), they often grow from an expanded base which surrounds the stalk as in corn, and branch off at regular intervals making knobs or joints, as may be seen in the bamboo cane (figs. 9 and 10), in other cases they branch off spirally, and when fallen form a sort of trellis-work on the stem (as in some of the palms) but always in a regular manner. The wood of this family of vegetables has the same porous structure as cane (figs. 11, 12, 13,14), and is often hollow in the centre, becoming more and more solid according to the age of the tree. The stems of these plants are limited in growth and soon acquire their full size, which never exceeds eighteen or twenty inches in diameter although some of the palms are nearly 150 feet high. When the stem has acquired its full size, the continual production of more woody fibres makes it impossible that these (like the exogenæ) can have a very extended period of existence, for when every part of the stem is full of woody matter, the plant ceases to grow from obstruction to the circulation of the juices. The stems of some of this family are always hollow like the stalks of corn; this arrangement allows of great elevations without bending, and is found to be the form which gives the greatest strength from a given quantity of material—one of those beautiful mechanical perfections of nature which man first admired and then endeavoured to imitate.
FIG. 8.—ENDOGENOUS LEAF,
SHOWING PARALLEL VENATION.
FIG. 9.—BAMBOO CANE,
SHOWING JOINT.
FIG. 10.—BAMBOO CANE,
SPLIT OPEN.
FIG. 11.—PERPENDICULAR SECTION
OF ENDOGENOUS WOOD.
FIG. 12.—PART OF THE SAME,
MAGNIFIED.
FIG. 13.—TRANSVERSE SECTION
OF ENDOGENOUS WOOD.
FIG. 14.—PART OF THE SAME,
MAGNIFIED.
Some of the palms and other endogenæ are of a most beautiful form, and are moreover quite as useful as beautiful, furnishing food to the inhabitants of many regions, especially the Arabs of the Desert, who carry the dried fruit of the Date-palm with them, on crossing these vast plains of sand, as their chief food. The Plantain (Musa sapientum) forms a most beautiful and graceful object, with its enormous leaves springing up from the ground by their midrib in clusters, and extending upwards for 20 or more feet in graceful curves, affording a shady and cool retreat beneath them from the burning rays of the sun; the fruit is also one of the necessaries of life in the regions where they abound. The Fan-palm is another beautiful specimen, from the fan-like leaves of which the punkahs or Indian fans are made. The Palmyra palm furnishes leaves which are used to thatch houses, the sap is drunk as a refreshing beverage, and when evaporated yields a kind of sugar called "juggery," from which palm-wine is made.
The palms were amongst the first trees created, their fossil stems being constantly found; they were even then associated with the elephant and rhinoceros, and although these are found chiefly in the northern parts of Europe, yet it is much more reasonable to suppose that the climate of these parts has changed, than that these two favourites of the sunny regions should have had their natures changed.
Among the useful members of the endogenæ may be mentioned the Maranta Arundinaceæ, or Arrow-root plant, which is thus described by Dr. Baird:—"It is a genus of monocotyledonous plants, belonging to the natural order Cannaceæ or Marantaceæ, and composed of herbs which have a well-developed rhizome or tuberous root containing a large quantity of fecula or starch. The species are natives for the most part, of tropical America, a few being also found in India. The structure of the flowers is remarkable, and the fruit fleshy. The most important species is the Maranta Arundinaceæ, a plant which is extensively cultivated in the West Indies, the southern parts of the United States, and in the Isle of France, for the sake of its root, which affords the substance so well-known as Arrow-root. This root consists of a tuber of a peculiar form, and contains a large proportion of fecula; the stem is upwards of three feet high, and the flowers are white, delicate, and small. In Cayenne the tubers are eaten by the natives, roasted, as a cure for intermittent fevers, and when bruised, are applied by them to wounds, and considered more especially as a specific against those caused by poisoned arrows, hence the name of Arrow-root."
According to Dr. Livingstone, the inhabitants of Angola live almost exclusively upon the Tapioca plant. He thus describes the mode of preparing it, &c.:—"They (speaking of the half-caste Portuguese) subsist chiefly on the Manioc, and as that can be eaten either raw, roasted, or boiled, as it comes from the ground, or fermented in water and then roasted or dried after fermentation and baked, or pounded or rasped into meal and cooked as farina, or made into confectionery with butter and sugar, it does not so soon pall upon the palate as one might imagine when told that it constitutes their principal food. The leaves, boiled, make an excellent vegetable for the table, and when eaten by goats, their milk is much increased. The wood is a good fuel, and yields a large quantity of potash.... The root, rasped while raw, placed upon a cloth, and rubbed with the hands while water is poured upon it, parts with its starchy glutinous matter, and this, when it settles at the bottom of the vessel and the water is poured off, is placed in the sun till nearly dry to form tapioca, the process of drying is completed on an iron plate over a slow fire, the mass being stirred meanwhile with a stick; when dry, it appears agglutinated into little globules, and is in the form we see in the tapioca of commerce."
Although none of this family of plants produce building timber (according to our notions of that article), yet it is questionable whether we have a greater number of uses for our exogenous woods than are found by the natives of those countries where the Endogenæ abound for palm stems and bamboo canes; as the Grecian styles of architecture arose from the imitation of structures of timber, so the Hindoo and Chinese styles have arisen from imitation of bamboo buildings. There is scarcely a constructive use that can be imagined to which this convenient material is not applied. In the "Penny Cyclopædia" (article "Bambusa") is the following:—
"The purposes to which different species of bamboo are applied, are so numerous that it would be difficult to point out an object in which strength and elasticity are requisite, and for which lightness is no objection, to which the stems are not adapted in the countries where they grow. The young shoots of some species are cut when tender, and eaten like asparagus. The full-grown stems, while green, form elegant cases, exhaling a perpetual moisture, and capable of transporting fresh flowers for hundreds of miles; when ripe and hard, they are converted into bows, arrows, and quivers, lance-shafts, the masts of vessels, bed-posts, walking-sticks, the poles of palanquins, the floors and supporters of rustic bridges, and a variety of similar purposes. In a growing state the spiny kinds are formed into stockades, which are impenetrable to any but regular infantry aided by artillery.
"By notching their sides the Malays make wonderfully light scaling-ladders, which can be conveyed with facility where heavier machines could not be transported. Bruised and crushed in water, the leaves and stems form Chinese paper, the finer qualities of which only are improved by a mixture of raw cotton, and by more careful pounding.
"The leaves of a small species are the material used by the Chinese for the lining of their tea-chests. Cut into lengths and the partitions knocked out, they form durable water-pipes, or by a little contrivance are made into excellent cases for holding rolls of papers; slit into strips they afford a most durable material for weaving into mats, baskets, window-blinds, and even the sails of boats. Finally, the larger and thicker truncheons are exquisitely carved by the Chinese into beautiful ornaments. It is however more especially for building purposes that the bamboo is important (fig. 15). According to Marsden, in Sumatra the framework of the houses of the natives is chiefly composed of this material. In the floorings, whole stems four or five inches in diameter are laid close to each other, and across these laths of split bamboo about an inch wide are fastened down with filaments of rattan-cane. The sides of the houses are closed in with the bamboo opened and rendered flat by splitting or notching the circular joints on the outside, clipping away the corresponding divisions within and laying in the sun to dry pressed down with weights. Whole bamboos often form the upright timbers, and the house is generally roofed in with a thatch of narrow split bamboos six feet long, placed in regular layers, each reaching within two feet of the extremity of that beneath it, by which a treble covering is formed. Another and most ingenious roof is also formed, by cutting large straight bamboos of sufficient length to reach from the ridge to the eaves, then splitting them exactly in two, knocking out the partitions and arranging them in close order, with the hollow or inner sides uppermost; after which a second layer with the outer or convex sides up, is placed upon the other in such a manner that each of the convex falls into the two contiguous concave pieces, covering their edges, the latter serving as gutters to carry off the rain that falls upon the upper or convex layer."
FIG. 15.—HUT OF BAMBOO.
The Endogenæ are divided into twelve orders, as follows:—
1. Graminacæ (Grasses).
Wheat, Barley, Meadow-grass.
The Graminacæ comprise the great bulk of those plants which supply man and the lower animals with food, for it contains all the grasses and corn-bearing plants, including rice, maize, wheat, oats, barley, and rye. Upon these all the Ruminants of the earth feed, and millions of human beings taste no other kind of food. There are nearly 4000 species of graminaceous plants, rice and maize being the most broadly extended, forming the chief food of the Chinese, Hindoos, and other nations; wheat is here the most valuable grain, and is now grown in all parts of Europe and America. Humboldt, in his "Views of Nature," gives an interesting account of the first wheat grown in New Spain. He says:—
"A negro slave of the great Cortes was the first who cultivated wheat in New Spain, from three seeds which he found in some rice brought from Spain for the use of the troops. In the Franciscan convent of Quito I saw, preserved as a relic, the earthen vessel which had contained the first wheat sown in Quito by the Franciscan monk Fra Jodoco Rixi de Gante, a native of Ghent in Flanders. The first crop was raised in front of the convent, on the Plazuela di San Francisco, after the wood which then extended from the foot of the volcano of Pinchincha had been cleared. The monks, whom I frequently visited at Quito, begged me to explain the inscription, which, according to their conjecture, contained some hidden allusion to wheat. On examining the vessel, I read in old German the words,
"'Let him who drinks from me ne'er forget his God.'
"This old German drinking-cup excited in me feelings of veneration. Would that everywhere on the New Continent the names of those were preserved who, instead of devastating the soil by bloody conquests, confided to it the first fruits of Ceres."
The third great natural family of plants are the Exogenæ. They comprise all the trees and shrubs of the temperate and colder regions, together with many of the flowering plants. They are characterised by certain peculiarities which can be at once recognised, such as the twisted and branched form of the stem, the possession of bark, leaves having the veins covering them running in all directions and forming a network, and the seeds containing two cotyledons; the wood, moreover, is deposited in rings (figs. 16, 17, 18, 19), one of which is formed every year, by the new wood being produced on the outside of the old, and between it and the bark. This deposition takes place as follows: after the rains of winter and early spring have well saturated the earth with moisture, and the warmth of spring has begun to penetrate to the roots of the plants, a development of the points of each fibrile or radicle takes place, forming new spongioles; these, being formed of new porous cellular tissue, begin to absorb (by endosmose) the moisture of the earth, which entering at all these thousands of minute spongioles at once, collects and rises in the vessels of the trunk and branches, and arriving at the vessels forming a plexis on the surface of every leaf, begins to be changed by the action of the sun's rays, absorbing carbon and giving out oxygen from the carbonic acid always contained in the air. The sap which has thus risen is the juice of the earth in which the plant grows, containing several earthy salts and vegetable extract drawn from the manure or decaying vegetation contained in the mould, together with carbonic acid dissolved in the fluid; this carbonic acid is changed by the sun's rays as well as that which was contained in the air, and the carbon uniting with the watery part of the sap, forms the green substance before alluded to, called chlorophyll, which is the green colouring matter of all plants, and is the basis of the wood. The altered sap descends between the wood and the bark, and forms a deposit gradually, which at the end of the year is a complete ring of wood surrounding the wood of former years. This circulation of juices continues through the summer, until, the cold weather coming on and the light being diminished, the sap neither rises nor is the leaf nourished by it, when it decays and falls off.
The age of exogenous wood can be ascertained—where the centre has not decayed—by counting the rings, one only being deposited every year; and it is truly astonishing to find that some trees will continue to live and flourish for several thousand years! There does not, in truth, appear to be any limit assigned to the life of an exogenous tree if it escape accidents; for, although decay inevitably attacks the heartwood, and a cavity is the result, yet, the new wood continuing to be deposited on the outer part, the vitality of the tree is kept up, and its size continues to increase.
The Baobab or Monkey Bread-fruit trees, growing at the mouths of the Senegal, have been estimated by Adinson to be upwards of six thousand years old, and are, in all probability, the oldest relics of organic life existing at the present time. The cedars of Lebanon are supposed to have existed longer than the records of history. The Yew at Braburn, in Kent, is at least three thousand years old; and that of Fortingal nearly as much.
Dr. Livingstone, describing the Mowana or Baobab tree (fig. 20), thus comments upon its power of withstanding injury:—
FIG. 20.—THE BAOBAB TREE.
"No external injury, not even a fire, can destroy this tree from without, nor can any injury be done from within, as it is quite common to find it hollow, and I have seen one in which twenty or thirty men could lie down and sleep as in a hut. Nor does cutting down exterminate it, for I saw instances in Angola in which it continued to grow in length, after it was lying on the ground. Those trees, called exogenous, grow by means of successive layers on the outside; the inside may be dead, or even removed altogether, without affecting the life of the tree; this is the case with most of the trees of our climate. The other class is called endogenous, and increases by layers applied to the inside, and when the hollow of the tree is full, the growth is stopped, and the tree must die. Any injury is felt most severely by the first class on the bark, by the second on the inside, while the inside of the exogenous may be removed, or the outside of the endogenous may be cut, without stopping the growth in the least. The Mowana possesses the power of both. The reason is, that each of the laminæ possesses its own independent vitality; in fact, the Baobab is rather a gigantic bulb run up to seed than a tree. The roots, which may often be observed extending along the surface of the ground forty or fifty yards from the trunk, also retain their vitality after the tree is laid low, and the Portuguese now know that the best way to treat them is to let them alone, for they occupy much more room when cut down than when growing."
On examining the wood of the exogenæ, it will be found that in the very centre is a small column of cellular tissue, called the pith, and that from this, fine layers of the same substance radiate towards the circumference. These are called the medullary rays, or silver-grain; they form an exterior layer or ring of cellular substance on the outside of the wood, which is called the cambium. The lightness of wood is owing to its porosity, and, on examining a transverse section under the microscope (figs. 17 and 19), it will be seen how little of real space is occupied in wood by solid substance. The spaces between the wall-work of woody matter in the tree are all filled with sap, and hence it is that "green wood" is so much heavier than that which is well seasoned. It is its lightness and strength, together with the ease with which it can be cut and fashioned, which renders wood so exceedingly useful; but its inflammability and liability to decay are great barriers to its more general use.
The leaves of the exogenæ have their veins always in the form of a network, and not running parallel with each other, as in the endogenæ (fig. 21).
Of the three divisions of the vegetable kingdom, the exogenæ alone furnish building timber, properly so called, and it is doubtful whether nature has supplied a more generally applicable substance than wood; being a bad conductor, it can be handled in the coldest weather, which metal cannot, and, being easily cut or split, can be fashioned into almost any form.
FIG. 21—EXOGENOUS LEAF, SHOWING RETICULATED VENATION.
The woods mostly in use for general purposes are the different kinds of pine, as American Pine, Norway Pine, yellow and white Deal, Mahogany, Oak, Beech, Elm, Ash, and Maple. In the "Penny Cyclopædia," under the article "Wood," is the following description of the different kinds used by cabinet-makers, &c.:—
"The woods that are used by the cabinet-maker for furniture of a more delicate kind are called 'fancy woods.' The use of these has become much more general since the introduction of the art of veneering, and now that this is done by machinery instead of by hand, a number of woods are used for furniture and other purposes, which, on account of their scarcity, could have been formerly used only to a very limited extent. The most common of the fancy woods, and that which is most used by cabinet-makers, is Mahogany. This wood is the produce of the 'Swienteria Mahogani.'
"Next in point of importance and use to Mahogany, is Rosewood. This wood obtains its name from its fragrance, and is the produce of a mimosa from the forests of Brazil; in veneering it affords about eight plates to the inch.
"King-wood is a beautiful wood much in use, brought from Brazil in logs four feet long and about five inches wide, and is used only for delicate articles; it is said to be the produce of a species of Baphia, a genus of Leguminous plants.
"Beef-wood is a very heavy wood of a pale red colour, and is brought from New Holland in logs nine feet long and thirteen or fourteen inches wide; the tree from which this is obtained is unknown to botanists, as well as most of those producing the fancy woods of commerce.
"Tulip-wood is brought into the market in very small pieces, not more than four feet long and five inches in diameter, so that probably it is the production of a shrub; it is clouded with red and yellow colours, and is used for bordering and for making small articles, such as caddies and work-boxes.
"Zebra-wood is probably the production of a large tree, as it is cheap enough to be made into tables, pianofortes, &c.; it is coloured brown on a white ground and clouded with black.
"Satin-wood is of a brilliant yellow colour with delicate glowing shades. It is the produce of a plant called Chloroxylon Swienteria, a native of India; it is one of the trees that yield the wood-oil of India, and belongs to the natural order Cedrelaceæ, the same order in which the mahogany is placed; it is found in the market in logs two feet wide and seven or eight feet long.
"Sandal-wood is the produce of a species of Sandoricum belonging to the family Meliaceæ; the wood is of a light brown colour with golden-coloured waves.
"Ebony and Iron-wood are the names given to some very hard woods, the produce of the natural order Ebenaceæ. These woods are mostly brought from India, although some of the species are found in Europe and America.
"There are several other woods occasionally used amongst cabinet-makers, of which little is known, either with regard to the places they come from, or the trees to which they belong. Canary-wood has a yellow colour; Purple-wood has a purple colour, without veins; Snake-wood is of a deep colour with black shades; Calander-wood is a handsome cheap wood taking a high polish, and is brought from Ceylon.
"Other woods are named after the places they come from, as Coromandel-wood, Amboyna-wood, &c."
Woods are largely used as dye-stuffs; the chief of these is log-wood, which has a deep red colour, is very heavy and solid, and yields a great deal of red colouring matter. It is very astringent, and contains tannic and gallic acids, from which properties it produces a deep black colour when mixed with any of the salts of iron; from this peculiarity it is very valuable as a black dye, but the black dye so extensively used for dyeing cloth, is, for the most part, made from galls, or "nut-galls," as they are sometimes called. These are hard round substances found growing on many species of oak, chiefly the "Quercus infectoria," and the best are brought from Aleppo; they are diseased growths produced by a little insect, called the "Cynips Quercus," which deposits its eggs under the epidermis of the leaf, and the juice collects and forms the gall (fig. 22), from the interior of which the larva eats its way out; thus it will be found that every gall must have a little round hole in it, whence the larva of the cynips has issued.
FIG. 22—ALEPPO GALL.
The root of the Madder plant (Rubia tinctorum) produces the most beautiful and permanent of our red dyes, and the cochineal insect (Coccus cacti) obtains its colour from feeding upon the cactus.
A useful and very permanent blue dye is obtained from Indigo, a kind of extract from the plant "Indigofera," growing in India and other places, and many other members of the vegetable kingdom yield dyes and colours used in the arts.
Amongst the various and almost endless purposes to which wood is applied, that of serving as a material to engrave on and print from must not be omitted. The wood used for this purpose is that of the box-tree (Buxus sempervirens), which furnishes a close, even-grained, hard wood, admirably suited to the purpose; and the cultivation and perfecting of this most admirable art, has produced an improvement in book-illustrating which can hardly be sufficiently appreciated.
Wood must have supplied one of the earliest materials with which to erect buildings; the Grecian styles of architecture, beyond doubt, were derived from imitating in stone those structures first made of wood. All the largest members of the vegetable kingdom belong to this division; and indeed the same may be said of size which has been said of age, namely, that there is no limit except from accidental circumstances.
FIG. 23.—WELLINGTONIA GIGANTEA.
In the Crystal Palace at Sydenham is a most wonderful and gigantic specimen of the Wellingtonia Gigantea (fig. 23), one of the class of trees called coniferous, and belonging to the exogens, the bark of which has been stripped off in portions at the place where it grew, each of which being numbered, has enabled them to be re-adjusted in their original places, the result of which is, the whole bark of this most magnificent tree appears as if growing on the timber. It measures 31 feet across at the base, and 93 feet in circumference; the original tree was 363 feet in height, its present height is 116 feet, and the bark is 18 inches thick. The Norfolk Island Pine (Araucaria excelsa) sometimes grows to 300 feet in height, and Humboldt, describing a specimen of the Pinus Trigona, says, "This gigantic fir was measured with great care; the girth of the stem at 6-1/4 feet above the ground was often 38 to 45 feet; one stem was 300 feet high, and without branches for the first 192 feet."
As the exogens grow by the addition of woody matter to their circumference, of course the older the tree (other conditions being equal) the larger will be the trunk, but as the new wood is added to the outside, the centre loses its vitality and is liable to the attacks of both animal and vegetable parasites, and is therefore constantly found either decayed or totally destoyed; this is not, however, invariably the case, and many instances are found of wood of a great age remaining sound in the centre. At St. Nicholas in Lorraine is exhibited a plank of walnut wood made into a dining-table which is twenty-five feet wide. Besides timber for various useful purposes, this division of the vegetable kingdom furnishes us with both cotton and linen for clothing, and many of the dye-stuffs for ornamenting such clothing, also with many articles of food (although not so prolific in this respect as the Endogenæ), the potato, most green vegetables, as cabbages, lettuces, are exogenous, together with such roots as carrots, parsnips, &c.
To this class of plants belong many of the most beautiful flowers, and all our fruit-trees, not the least important of which is the fig-tree, although the fig can hardly be called a fruit in the strict sense of the word, being a consolidated mass of flowers within a receptacle. The figs of commerce are produced from the Ficus carica, the fruit being dried in the sun; they form a considerable article of commerce. The celebrated Banyan tree (Ficus indica, fig. 24) is one of the fig tribe, it throws down branches (as do many others of this tribe) which take root in the earth and form fresh stems, so that one of the banyan trees with its off-shoots will cover a space of ground sufficient to shelter a regiment of cavalry, and many of the fig tribe, especially the sycamore (Ficus sycamorus), are planted for the sake of the shelter they supply by their broad crowns of leaves; another of the fig trees (Ficus elastica) supplies a great part of the India-rubber of commerce.
FIG. 24—THE BANYAN TREE.
De Candolle divides the class of exogens into four sub-classes according to the arrangement of their flowers &c.; they are as follows:—
1. Thalamifloræ, the flowers of which are furnished with both calyx and corolla, the corolla having distinct petals, and the stamens hypogynous, that is, growing immediately from below the pistil.
2. Calycifloræ, having flowers with both calyx and corolla, the corolla divided into distinct petals, but the stamens always Perigynous, that is, growing upon the sides of the calyx.
3. Corollifloræ, having flowers with both corolla and calyx, the former having its petals united.
4. Monochlamydeæ, flowers without corolla and often without a calyx.
These four sub-classes have been divided into orders as follows:—
Orders of Thalamifloræ.
1. Nymphaceæ (Nymphæa alba) White Water-Lily.
(Nuphar luteum) Yellow Water-Lily.
This order contains water plants of great beauty, they grow in the mud at the bottom of the water, sending up long flower- and leaf-stalks so that the flowers may blossom in the air and the leaves float on the surface; the leaves are generally round and turned up slightly at the edges. The "Victoria Regia" is a magnificent specimen of this order; it originally came from Brazil, and has flowers a foot wide, leaves four or five feet across, and is sufficiently buoyant, it is said, to bear the weight of a child. The Lotus of the Nile, the blossom of which so frequently occurs on the carvings of the Egyptians as an offering to Isis, is another member of this order.
White Water-Lily.
2. Papaveraceæ (Papaver somniferum) White Poppy.
(Papaver Rhœas) Red Poppy.
White Poppy. Red Poppy.
Opium is prepared from the unripe capsules of the White Poppy, it is chiefly cultivated for this purpose in India and Turkey. The Chinese are the great consumers of opium, it being a common habit with them both to eat and smoke it. Opium is made by collecting the juice in the morning which has exuded from incisions made in the capsules over night; those employed for this purpose use a small knife with several blades and go round the plantations scarifying the capsules in the evening, and the juice which issues and forms a thick concrete matter, is scraped off, beaten up, and dried in round lumps. About £2,000,000 worth are exported from India annually.
14. Malvaceæ (Malva sylvestris) Common Mallow.
(Althæa officinalis) Marsh Mallow.
Marsh Mallow.
The Marsh Mallow has been much esteemed as a demulcent medicine, and an ointment is made from it for external use; but one species of this order, the Gossypium, is one of the most important plants in the whole world, producing that most useful article, cotton, so largely grown in America, and for which the slave population are chiefly employed. The fine white hairs surrounding the seeds and filling up the pod is the part picked out and preserved, it forms the cotton-wool of commerce, of which some eight hundred millions of pounds' weight are used annually! employing a million and a half people, in England alone, and furnishing clothing to hundreds of millions. It is grown in India, which is supposed to be its native place, and will probably be grown to a much greater extent when railways and canals shall have made a more easy communication from the interior of that country to the sea-board.
15. Geraniaceæ (Geranium pyreniacum) Meadow Geranium. | |
Meadow Geranium. | Many species of this order are indigenous, and when cultivatedproduce some of our most beautiful garden flowers, as the Geraniums,Pelargoniums, and Erodiums. The Geraniums are those species whichhave five irregular petals and ten stamens; they are the mostcharacteristic of the order. |
16. Linaceæ (Linum usitatissimum) Common Flax.
Flax Plant.
The Flax plant is another of those insignificant plants which, from certain properties they possess, have become the greatest boons to mankind; the stalks of the Linum usitatissimum, soaked, bruised, and prepared by combing, &c., form the flax of commerce, from which all our linen fabrics are made. The manufacture of flax is one of the oldest arts known, the ancient Egyptians formed their mummy-cloths from this article, and a piece of one of these cloths, bleached and placed side by side with some of the present date, would hardly suffer by the comparison, but the rapidity of its manufacture, and the price at which supplied, are doubtless very different in the two cases.
The value of the linen manufacture of Great Britain is between seven and eight millions yearly.
The seeds of the flax plant (Linseed) are used to crush and produce the linseed oil of commerce so extensively used in the production of paints and varnishes, and the cake is used as food for cattle.
This completes the orders of Thalamifloræ, which, with the following sub-class, Calycifloræ, contain all our star-like flowers, or those in which the corolla forms a whorl or open ring of petals. The third sub-class contains those chiefly in which the flowers form cups or bells.
Orders of Calycifloræ.
4. Rosaceæ (Rosa centifolia) Hundred-leaved Rose.
(Fragaria vesca) Wood Strawberry.
(Rubus fruticosus) Bramble.
(Pyrus communis) Pear Tree.
Pear Tree. Rose. Strawberry.
This important order yields us our most beautiful flower, the Rose, of which there are a great many varieties, among which the Dog-rose—that beautiful ornament to our hedges—deserves to hold a conspicuous place, also the Sweetbriar or Eglantine. The rose is used in Turkey and Persia for obtaining that most valuable and delicious perfume, "Otto of Roses." It is made by distilling a portion of water from several quantities of fresh roses, until it becomes saturated with the volatile oil. This water is then exposed to the open air, and, in the cool night time, drops of the otto collect on the top, from which it is carefully gathered, and the same water again distilled from a fresh quantity of roses. Besides the Rose tribe, this order contains some of our most valued fruits. The Apple, Pear, and Strawberry belong to it, also the Almond.
Orders of Corollifloræ.
15. Solanaceæ (Atropa belladonna) Deadly Nightshade.
(Solanum tuberosum) Potato.
(Capsicum annuum) Capsicum.
(Hyoscyamus niger) Henbane.
(Nicotiana Tabacum) Tobacco.
Tobacco.
A great many members of this order are poisonous, among which the Deadly Nightshade (Atropa Belladonna) is the most virulent, there are also Henbane and Tobacco, both strong poisons; but, to compensate for this bad character, the order contains one of the most useful vegetables used in Europe—the Potato. This is the tuber of the "Solanum tuberosum." The following account of the introduction of the Potato into England is from the "Penny Cyclopædia":—
"Queen Elizabeth, in 1584, granted a patent 'for planting and discovering in new countries, not possessed by Christians,' and, under this sanction, some ships, principally equipped by Sir Walter Raleigh, sailed with him to America. Thomas Harriott (afterwards known as a mathematician) who accompanied the adventurous squadron, transmitted to England the description of a plant, called Openawk by the natives of that part of America, which the courtier-like gallantry of Raleigh had named 'Virginia.' Harriott described the Openawk as having the roots round, and 'hanging together as if fixed on ropes, and good for food either boiled or roasted.' Girarde in his Herbal a few years subsequently, distinguished the plant by a plate, and not only confirmed the assertion that it was an indigenous production of Virginia, whence he himself had obtained it, but supplied some curious details of its qualities, and of the various modes in which it might be dressed for the table. But the Potatoe had been known in Spain and Portugal at an earlier period, and it is from the latter country that we most directly derive the name by which we know it. This is easily shown; although the natives of South America called the plant by the name 'Openawk,' those of the South, more particularly the inhabitants of the mountains of Quito, called it 'Papas,' which the Spaniards corrupted into 'Battata,' this again their neighbours in Portugal softened into 'Ba-ta-ta' (da terra), to which 'potato' is a very close approximation."
This plant, the tubers of which for a long time were a luxury obtainable by the rich only, now yields the support of the poor, and furnishes the cheapest food known; the peasantry of Ireland almost subsist upon Potatoes, and the poor of most parts of Europe find it indispensable to their living.
Orders of Monochlamydeæ.
6. Corylaceæ (Castanea vesca) Sweet Chestnut.
(Quercus pedunculata) Oak.
(Corylus avellana) Hazel Nut.
Sweet Chestnut.
This order contains some of our finest trees; the Oak, that prince of trees, is of this order. It attains a great age and size, and there are some celebrated specimens existing which have stood many centuries. Oaks constitute the greater part of the forest trees, both on the Continent and in England; great numbers are cut in France for fire-wood, and in both countries for ship-building. The roof-timbers of our old churches and halls are nearly all oak. The bark of the oak is largely used for tanning leather. About 30,000 tons are imported into this country yearly for this purpose, besides the product of our own trees. The bark of the Cork-oak (Quercus suber) is used for making corks, some 2,000 tons of this are imported annually. Moreover, the Gall-nut used in tanning, and also to make black dye, is the product of an oak. The Chestnut is a fine tree, the nuts of which are commonly eaten by the peasantry of Spain and Italy as food; the tree grows to a great age and to an enormous size.
It is from the vegetable kingdom that most of the medicines in use are derived, but many of these, in improper doses, act as violent poisons; indeed, the most rapidly fatal of all poisons, prussic acid, was originally distilled from the Laurel-cherry, and strychnine, which is hardly less rapid, is the produce of the Nux vomica (Strychnos nux vomica).
The following is a list of the principal poisonous plants found growing wild in England:—
Those marked (*) in the foregoing list are acrid poisons, and the remainder are narcotic.
OAKS.
Out of these three great families of plants, in their almost endless variety of size, form, and colour, it has pleased the Great Author of Nature to form all the vegetation which beautifies this earth, from the lofty Palm—which, from its grateful freshness and the beauty of its structure, seems almost as if possessed of more than vegetative life, to the Algæ, which form "the pool's green mantle"—from the gigantic and "storm-defying" Oak, with its green foliage spreading out far above, and throwing its welcome shade around, to defend from the sun's rays the gentle deer who pasture on the herbage beneath—to the grass and clover, and the sweet-smelling wild flowers at their feet—
"Daffodils
That come before the swallow dares, and take
The winds of March with beauty; violets dim
But sweeter than the lids of Juno's eyes,
Or Cytherea's breath,—pale primroses
That die unmarried, ere they can behold
Bright Phœbus in his strength"—
form inexhaustible themes on which to exercise our faculties of admiration, and which serve admirably to minister to those wants which, without doubt, were given to us that we might derive pleasure from their being thus beautifully gratified—themes for the pencil of the artist, who "holds, as it were, the mirror up to nature," and the architect, when he designed his vistas of slender columns spreading out into and supporting roofs of tracery, might well be supposed to have had in his "mind's eye" some beautiful recollection of the arcades of Nature's palaces in the sombre forests, where the twisted trunks of the trees, the fretwork of their branches, and the leafy covering formed by their leaves, supply all the requisites of a grand and lofty temple, fit for the worship of that great First Cause who formed them.
FOREST SCENE.
[THE ANIMAL KINGDOM.]
FIG. 1.—ANIMALCULÆ FOUND IN STAGNANT WATER.
| A, Cyclops Quadracornis. | F, Ambœba princeps. |
| B, Anguillula. Fluviatilis. | G, Acineta mystacina. |
| C, Actinophrys. Sol. | H, Oxytrycha. |
| D, Coleps Hirtus. | I, Triophthalamus dorsalis. |
| E, Vorticella. | J, Polyarthra. |
After considering the beautiful covering which a kind Providence has given to the earth in the form of all sorts of vegetation, it will be necessary now to consider for what kind of creatures this most delightful garden was prepared, whether they seek their food in the air, water, or earth, for all these places are abodes of the vegetable tribes, and where there is vegetation there are animated beings; for there is not an animal in existence, but directly or indirectly feeds upon the vegetable kingdom, from the elephant and rhinoceros which devour whole plantations, to the minute animalculæ which float in the air or dwell in every drop of stagnant water, where food in the form of equally minute algæ is found—each possessed of wonderful organs and powers suitable to the kind of existence they lead, for God has often placed life in the most simple as well as complicated forms. Dr. Mantell says:—
"We have been accustomed to associate the presence of vitality with bodies possessing various complicated organs for the elaboration and maintenance of the energies of existence, but here we see perfect and distinct creations in the condition of globules and cells, which live and move and have their being, and increase in numbers with a rapidity so prodigious, and in modes so peculiar, as to startle all our preconceived notions of animal organisation."
And it is in these Protozoa, the lowest of the animal creation, that a perfect similarity of condition exists to those of the vegetable kingdom, they are here upon a level; but arising out of these simple forms, God has created two sets of types or portraits, the members of each resembling those below it in some particular, but having organs which are superior to it; and above these are found members whose organs are of a still higher order, and so on till the one set comprises the highest orders of the vegetable, and the other those of the animal kingdom, in its ranks. But these simple organisms are never developed so as to resemble those placed above them; they each, whether high or low, continue to produce their like, for each grade was a creation of itself and a separate one from God's hands. There have been writers, who would endeavour to make it appear that God only created the lowest and most simple germs, and the circumstances which were necessary to develop them, and then allowed these to act and re-act until a man or an oak tree at last became the result! Were this the case, geology would long before this have shown the "small beginnings" of man; but no! as soon as traces of man's creation are perceived, he is found as perfectly formed and organised as he is now, there are no transition stages of man's existence, nor of any other animal. It is true that the simpler forms of both animal and vegetable existence were created first, but this was in accordance with the state of the earth's surface, which was not at first suitable to the requirements of the higher animals, which were only created when the earth was in a state suitable to receive them.
But when the surface of the earth was still more developed God created man. His last and greatest work; and there can be no doubt that God in His wisdom caused all these changes to precede the creation of man, that he might lack nothing to confer happiness on him, nor objects to exercise his faculties upon.
Animals are divided into two great natural families, the Invertebrate and the Vertebrate, the former having neither spine nor internal skeleton, the latter having both.
The Invertebrate animals are divided into the following sub-families, classes, and orders by Dr. William Carpenter.
| Sub-family 1.—Radiata, having Four classes. | ||||
|---|---|---|---|---|
| 1. Infusoria. | ||||
| 2. Entozoa. | ||||
| Hydroida |
| ||
| 3. Zoophyta. | Asteroida | 4 Orders. | ||
| Helianthoida | ||||
| Ascidioda | ||||
| 4. Radiaria. |
| Acalephæ |
| 2 Orders. |
| Echinodermata | ||||
| Sub-family 2.—Articulata, having Five classes. | ||||
| 1. Annellata. | ||||
| 2. Cerripeda. | ||||
| 3. Crustacea. | ||||
| Coleoptera |
| ||
| Orthoptera | ||||
| Neuroptera | ||||
| Hymenoptera | ||||
| 4. Insecta. | Strepsiptera | 9 Orders. | ||
| Lepidoptera | ||||
| Hemiptera | ||||
| Diptera | ||||
| Aptera | ||||
| 5. Arachnida. | ||||
Sub-family 3.—Mollusca, having Six classes.
| Acephala, or Headless. | Encephala, Having a Head. |
|---|---|
| 1. Tunicata. | 4. Pteropoda. |
| 2. Brachiopoda. | 5. Gasteropoda. |
| 3. Lamellibranchiata. | 6. Cephalopoda. |
The Infusoria, the first class of the Radiata, comprise all those microscopic organisms called "Protozoa;" they consist of a membranous cell with fluid contents, and are very nearly allied to the Protophytes or lowest vegetable existences. It is still a matter of discussion amongst physiologists and microscopists as to which kingdom shall claim certain of them, but, according to Dr. Carpenter, it appears that the vegetable cell-beings have two envelopes, the inner one albuminous and the outer one cellulose or starchy, and the following passage occurs in his treatise on the Microscope (which should be in the hands of all enquiring minds):—
"The animal cell, in its most complete form, is comparable in most parts of its structure to that of the plant, but differs from it in the entire absence of the 'cellulose wall' or of anything that represents it, the cell-contents being enclosed in only a single limitary membrane, the chemical composition of which, being albuminous, indicates its correspondence with the primordial utricle. In its young state it seems always to contain a semi-fluid plasma, which is essentially the same as the protoplasm of the plant, save that it does not include chlorophyll granules, and this may either continue to occupy its cavity (which is the case in cells whose entire energy is directed to growth and multiplication) or may give place, either wholly or in part, to the special product which it may be the function of the cell to prepare. Like the vegetable cell, that of animals very commonly multiplies by duplicative sub-division, it also (especially among Protozoa) may give origin to new cells by the breaking up of its contents into several particles."
Some of these creatures are so exceedingly minute that hundreds of millions may be contained in a drop of water. They have no organs of any kind, but consist of single cells of a soft substance called "sorcode;" there is no distinction of sexes, and generation takes place by sub-division, each cell separating into two, and these again into two more, and so on with marvellous rapidity; this is the usual method of increase, but occasionally an act of conjugation takes place, two cells blending into one at the points of contact, the result of which is a nucleus or cell within the original one. These animated cells are of all forms, having prolongations which appear to be thrown out to absorb any particle of organic matter within reach, which then enters within the soft substance of the animalcule and is digested or dissolved, such are the Ambœba, the Actinophrys, &c. (see fig. 1); a step or two higher from these, the very lowest, infusoria are found to possess the first rudiments of organs in the form of cilia, which consist of minute elongations having a constant vibratory motion, for the purpose of causing a current in the water in which they live and bringing food into their vicinity.
Some very curious and complicated changes take place in the lowest of the animals, very similar to those in the lowest vegetables; and what has been called the life-history of these beings, often embraces a great number of forms before the circle of their metamorphoses comes round to the starting-point. Some of these phases of existence are quite different from those going before and after them, and as the vegetable free-cell at one time is capable of motion, it has long been mistaken for an active living animalcule (the Protococcus pluvialis, &c.), and there can be no doubt but that it will be found that many of the lower forms of animated life described by Ehrenberg and others, and still considered as such, will prove to be merely different stages of the metamorphosis of the same protozoon; or it may be not an animal at all, but a simple vegetable or protophyte.
FIG. 2.—VOLVOX GLOBATOR.
Dr. Carpenter says, "It is quite certain that the Desmidiaceæ, like the confervoid plants in general, grow at the expense of the inorganic elements which surround them, instead of depending upon other living beings for their subsistence, and that they decompose carbonic acid and give off oxygen under the influence of sunlight. They have the power of generating from these materials the organic compounds which they require for their own development, and these are such as are formed by other undoubted protophytes, as is proved by the application of the appropriate tests." These "Desmidiaceæ" were long considered to belong to the animalculæ, as were the "Diatomaceæ," "Volvox globator" (fig. 2), &c.
FIG. 3.—WHEEL ANIMALCULE.
Some of the Infusoria, however, have a far higher organisation, such as the "Rotiferæ," and especially the "wheel animalcule" (fig. 3), which at one time was supposed, absurdly enough, to possess a living wheel turning round rapidly on its head! This wheel, however, proved to be nothing else than a vortex of water produced by rotatory cilia. This and many other mistakes were owing to the imperfect construction of the microscopes of that date. These and their fellow animalcules possess several organs, as a stomach, &c. The protozoa at one time were supposed to possess a number of stomachs, and were thence called "poly-gastric infusoria," but it has now been demonstrated that these beings merely absorb or entangle portions of organic matter into their substance, and that there are no cysts or stomachs for their reception. Some of the Infusoria are able to withstand enormous changes of temperature, without losing their vitality; cold far below freezing point, and heat equal to boiling water does not destroy them, and they may be dried in the most complete manner which chemists can devise, and kept in this dry state for years, and yet, on the application of moisture, return to life. There is no doubt but every inch of air contains the germs of some of the Infusoria in a dry state or their ova, and make up a portion of that fine halo of dust which always appears in the air when a gleam of sunshine is let into a dark place.
The second class of the Radiata, the Entozoa, are those beings which inhabit, as parasites, the intestines and other parts of animals. Their history is very obscure, but there seems to be about twenty varieties of these creatures, and a great number of animals have their peculiar Entozoa. The best known in the human subject are the "Ascaris" or thread-worm, the "Lumbricus Teres" or long-worm, and the "Tænia" or tape-worm; this last is jointed, and grows to several yards in length.
FIG. 4.—SERTULARIA OPERCULATA (a, Natural size, b, magnified).
FIG. 5.—FRAGMENT OF SPONGE, MAGNIFIED.
The third class, the Zoophyta, includes four orders. The first of these, the Hydroida, comprise the Tubularia, Sertularia (fig. 4), and Sponges (fig. 5); these are minute gelatinous creatures, secreting a sort of tube in which they dwell. These tubes are congregated into masses of different forms and colours, and, with other structures totally different, are erroneously known by the general name of "sea-weed." The Zoophyte which dwells in these tubes is furnished with a set of cilia forming a sort of plume. Most of these Hydroida are phosphorescent, such are those which, scattered about on the surface of the sea, contribute to that luminosity so frequently seen.
FIG. 6.—GORGONIA GUTTATA (Natural size).
The second order of the Zoophyta, Asteroida, are those which have a star-like shape; they are congregated into compound structures, forming what are called sea-fans (Gorgonia, fig. 6). These Gorgonia are of all colours, and very beautiful; the animals or "polypes" are gelatinous, and have a gelatinous mass or stalk with branches, strengthened and supported by a horny centre. This gelatinous mass forms the animal itself, as well as a sort of common integument connecting the whole family of many thousands. The Gorgonia or sea-fans usually preserved, are dry and hard, as the gelatinous covering has so little substance that, when dried, it forms a rough powdery covering only to the horny support. This powdery surface, if washed off with a little water and placed under the microscope, is found to contain and be made up of spiculæ or crystals of carbonate of lime, of various colours and beautiful forms (fig. 7); these, when the animal is alive, help to support its gelatinous frame; the Tubiporæ also belong to this class. Fig. 8 represents the Organ-coral (Tubipora musica); it is of a bright red colour, and, when the polypes are living, is a very beautiful object.
FIG. 7.—SPICULES OF GORGONIA, MAGNIFIED.
The third order of Zoophytes is the Helianthoida, which include the "Actinia." These Zoophytes are entirely gelatinous, and have beautiful variations of colour. They throw out tentacles like the petals of a flower, and form very beautiful objects; they may be seen in the aquatic vivaria of the Zoological Gardens. To this order of Zoophytes belong the "corals" or Zoanthoid polypes, which produce the coral reefs, extending in some cases hundreds of miles. Dr. Baird gives the following account of them:—
"By far the greater part of the Zoanthoid polypes, as they grow, deposit in the cellular substance of the flesh of their back an immense quantity of calcareous matter which enlarges as the animal increases in size, and, in fact, fills up those portions of the substance of the animal, which by the growth of new parts are no longer wanted for its nourishment, and in this manner they form a hard and strong case, amongst the folds of which they contract themselves so as to be protected from external injury, and by the same means they form for themselves a permanent attachment which prevents their being tossed about by every wave of the element in which they live. The stony substances so formed are called corals, and their mode of formation causes them exactly to represent the animal which secretes them. The upper surface is always furnished with radiating plates, the remains of the calcareous particles which are deposited in the longitudinal folds of the stomach. These, in all probability were the constructors of all the strata of limestone rocks, which form some of our largest mountains—they were once the beds of seas, and were up-heaved by internal forces. The Madrepores (fig. 9) are also of this order, and form the stony matter in the same way. These are of various patterns, and the beautiful brain-stones in the British Museum are of their construction."
FIG. 8.—TUBIPORA MUSICA.
The fourth order of Zoophytes are the Ascidioida, including formerly the Flustræ (fig. 10), but of late these have been shown to be closely allied, if not identical with, the Tunicated Mollusca, and have received the name of Polyzoa, they will therefore be noticed under that head.
FIG. 9.—CORAL (Madrepora brachiata).
FIG. 10.—SEA MAT (Flustra foliacea), (A, magnified, B, natural size).
The fourth class of the Radiata, are the Radiaria, including two orders. The first of these are the Acalephæ; the Medusæ or Jelly-fishes belong to this order; these creatures float about sometimes in great numbers, they are transparent and gelatinous, of a hemispherical form, the flat surface being fringed round with fibres, some of which sting like nettles if brought into contact with the skin.
The second order of the Radiaria include the Echinodermata or Sea-hedgehogs, Star-fishes, &c., these are many of them furnished with a profusion of spines, and hence their name; they are also called Sea-eggs or Sea-urchins (fig. 11), and are mostly of a conical or spherical shape, divided into five segments covered with minute holes, from which project tentaculæ serving as organs of locomotion, touch, &c., and the surface of the body is covered with shelly spines of various forms and thicknesses; the mouth is in the centre, and they feed upon marine productions. The spines, if cut across and ground thin so as to be transparent, show a most complicated and beautiful structure when under the microscope (fig. 12).
FIG. 11.—SEA-URCHIN (Echinus), WITH AND WITHOUT SPINES.
FIG. 12.—SPINE OF ECHINUS (A, natural size, B, a section magnified).
The Star-fishes are inhabitants of the sea, and have generally five arms covered beneath with tentaculæ having small suckers at the point, it is by means of these that they move from place to place; the mouth is in the centre. They live upon small marine animals, and have the power of reproducing any of the rays which happen to be broken off; and if cut into two or more pieces, each will produce a fresh animal. There is a species of Star-fish, so brittle, that it is quite impossible to touch it without breaking it, or rather it breaks itself, for it seems to have the power of casting off its arms at pleasure. These forms complete the Radiate series of animals, they have nearly all a somewhat regular radiated form, and some of them are very beautiful, such as Sertularia, which grow in communities and form many beautiful branched objects, much resembling sea-weeds and flowers, hence the name Zoophyte, which means animal flowers.
FIG. 13.—EARTH WORM (Lumbricus terrestris), LEECH (Hirudo medicinale).
The Articulata form the second division of the Invertebrata. It has five classes, the first of which is the Annellata; in this order are included the Worms and Leeches (fig. 13), these have no hard covering but are soft throughout, they are made up of a number of soft rings which encircle their bodies from one end to the other, and are capable of being shortened or elongated by the muscles which draw together the rings (these are placed longitudinally), or by those which contract and widen them, placed circularly; this enables them to move along, and in so peculiar a manner that it has received the name of "vermicular," or worm-like. The most familiar example of this class is the Earth-worm (Lumbricus terrestris), this lowly creature lives in soft mud and clay and bores its way into the ground, in doing so it is assisted by a slimy secretion which covers it, its food consists of earth containing organic matter, this it swallows constantly and extracts what is fit for its nourishment ejecting the remainder apparently unaltered; the curious little heaps of soft dirt which are so often seen in wet weather on the garden-paths, &c., are formed in this way. The Leech is another familiar example of the Annellata or Annelidæ, this little useful creature lives in ponds and stagnant waters, and feeds by sucking the fluids of other animals (chiefly frogs and fish) with which it will gorge itself till it is double its original size, it will then remain (often for months) without food till it is all appropriated, the process going on very slowly; a full-grown Leech is perhaps twenty years old, they grow so slowly, (hence it is, that Leeches may be kept for months after being gorged with blood without any food, and they will live and be healthy). They are furnished with two suckers, one at each end, and a mouth with numerous fine teeth placed in a tri-radiate manner, with which they pierce the skin when about to feed. They move in the water with great rapidity by a wavy motion of their bodies, but on solid substances their mode of progression is that of adhering by the sucker in front, then drawing the other one close up and extending the body to its full length, taking hold again by the front sucker and again bringing up the hindermost.
The Cirripeda constitute the second class of the Articulata, which comprise the "Acorn shells" and "Barnacles" (fig. 14); these little creatures were formerly described as Molluscs, but are now considered to be articulate animals, and by some as Crustaceans. Dr. Baird gives the following description of them:—"The Cirripeds are articulated animals contained within a hard covering composed of several pieces and consisting of calcified chitine. The body of the animal is enclosed in a sac lined with the most delicate membrane of chitine, which in one group is prolonged into a peduncle and contains the ova; the body is distinctly articulated and placed with the back downwards."
FIG. 14.—A, SEA-ACORNS; B, BARNACLES (Cirripedes).
Dr. Carpenter describes the young of the Cirripedes as not fixed like the adult creatures, but moving about freely, and only becoming fixed in the form of the usual acorn shell after undergoing several strange metamorphoses, during which stages they more resemble the ordinary Crustaceans than they do in their fixed state.
The Crustacea form the third class of the Articulata, they comprise animals covered with a hard shell or carapace, like a case made up of rings, with joints allowing the pieces to move upon each other, except where several of them are consolidated to form the principal covering. These rings generally amount to twenty-one in number, some composing the claws, others the legs, &c. The shell is chiefly made of carbonate of lime (chalk) held together by animal matter. The greater part of the Crustacea inhabit the waters, and they cast their shells from time to time as they grow; the Lobster (Astacus marinus), is a familiar example, it is found in the sea near rocky shores, and is capable of rapid motion under the water, darting along (tail foremost) with great rapidity, it has powerful claws, with one of which (the blunt one) it holds its food and with the other (the sharp one) cuts it up into pieces; they have the power of casting off these claws and reproducing them; they feed upon smaller Crustacea and fish, or any animal matter they can find. The Cray-fish is another example, it is a sort of fresh-water Lobster, living in holes (frequently deserted rat holes) in the banks of rivers; its shell is very rough, but otherwise somewhat resembles the Lobster. Crabs, Shrimps, and Prawns, are members of this class (fig. 15).
FIG. 15.—CRUSTACEA.
| 1. Lobster (Astacus marinus). | 3. Crab (Cancer pagurus). |
| 2. Cray-fish (Astacus fluviatilis). | 4. Shrimp (Crangou vulgaris). |
| 5. Prawn (Palæmon serratus). | |
FIG. 16.—INSECTS.
| 1. Dragon-fly (Libellulina depressa). | 4. Fly (Musca domestica). |
| 2. Grasshopper (Gryllus). | 4. Butterfly (Pontia brassicæ). |
| 3. Bee (Apis mellifica). | 6. Musk-beetle (Cerambyx moschatus). |
The Insects form the fourth class of this division, and by far the most important and numerous. They come to maturity only after undergoing successive changes from the egg to the perfect animal; these transformations are amongst the most wonderful things connected with them. The eggs (some of which are very beautiful) are first deposited in some safe place, either attached to a leaf or tied up in a small bundle by silken threads spun by the parent insect, and in some nutritious substance, so that when it comes to life it may at once have food; this is sometimes in manure, sometimes in flesh, and sometimes under the skin of a living animal (few are exempt from this infliction), where they remain for a time and then come forth as maggots, caterpillars, &c.; in this state they are called "larvæ," these are generally active creatures and eat most voraciously, which seems to be the principal act of this state of their existence. These larvæ frequently change their skins as they grow, and at last they assume the next stage of their life, the pupa or chrysalis state, which is one generally of complete inactivity; many of these larvæ, weave themselves a covering of a sort of silk, to defend them while in the pupa state—such as the Silkworm, whose covering (cocoon) is the source of all the silk of commerce—others merely place themselves in a situation of security. The pupa remains dormant for a certain time, and then becomes the imago or perfect insect (the last state of its existence), such as a Moth, a Butterfly, a Beetle, &c. These are of different sexes, and in due time produce a batch of eggs and then die; these eggs are often incredible in numbers, amounting to many thousands—fortunately but few escape the watchful eyes of other insects and of birds who feed upon them.
FIG. 17.—ANTENNA OF COCK-CHAFFER
(Melolontha vulgaris).
FIG. 18.—FOOT OF FLY, MAGNIFIED.
FIG. 19.—SPIRACLE.
Insects have six jointed legs, a pair of antennæ or horns (as they are called) and generally one or two pairs of wings. The head is joined to the body by a constricted neck, the part of the body to which it is joined is called the thorax, and to this is added the posterior part or abdomen; this part is extremely various in form in different insects, in some it is round and full, in others long and extended. The antennæ arise from the head, and are generally composed of eleven pieces variously disposed; these wonderful organs are possessed of great sensibility, and they certainly serve to convey information to the insect, of the nature of one of the special senses; it was formerly thought to be simply that of touch very much refined, or of smell, but it is now generally considered to be that of hearing, or a modification of it. The forms of the antennæ are very various, fig. 17 represents that of the Cockchaffer (Melolontha vulgaris). The legs proceed from the thorax, as do the wings, the abdomen giving rise to none of the extremities; the feet of insects are all pretty much upon the same model, some being more developed than others, they have a pair of hooks or claws for catching and clinging to rough surfaces, and a pair of cushions or pads, covered in some cases with suckers. The foot of the Fly (fig. 18) is well developed in this particular, enabling it to walk with perfect ease even on glass or the smoothest surface, and in any position. Insects do not breathe by lungs or gills, but by means of branched tubes called "tracheæ," which convey the air to the interior of the animal. On the surface of these, the blood vessels ramify, giving out the carbonic acid of the blood and receiving oxygen; the openings to these air-tubes are arranged along the sides of the body, and are called "spiracles" (fig. 19). They are curious objects under the microscope, some of them being closed by a perforated membrane, others have a sort of sieve or network of fibres, and most of them a contrivance to catch and exclude minute particles of matter floating in the air, and thus prevent their entry into the tracheæ. Insects have two eyes, one on each side of the head, which are of great size, often forming complete hemispheres; each eye is made up of several thousand separate eyes or "ocelli," hence they are called compound eyes; these ocelli are placed closely together, so as to form a sort of honeycomb arrangement; the appearance of a part of one of these eyes is shown in fig. 20.
FIG. 20.—COMPOUND EYE.
(1, perpendicular section; 2, surface.)
Insects are amongst the most active of creatures, whether for good or for evil, and the prodigious rapidity with which they increase under favourable circumstances would soon cause them to overrun the whole earth, to the extinction of almost every other creature, were these circumstances not controlled by an all-wise Providence, who keeps a constant check upon their progress by causing one insect to feed upon another, and who has formed almost innumerable other creatures (including birds, reptiles, and fishes) with instincts which lead them to feed upon insects in every stage of their development (fish devour the larvæ of many insects which inhabit the waters during the first stage of their existence); but it occasionally happens, when some of these salutary checks upon their increase are withdrawn, that they multiply with such fearful rapidity as to produce a complete famine, for they eat up everything before them. Who has not heard of the plagues of Locusts and the depredations of the White Ants? The swarms of Locusts in Africa will sometimes cover many hundred square miles of surface, and in this space not a vestige of any vegetation would remain after their visit. The description of the prophet Joel is sublime: "The land is as the garden of Eden before them, and behind them a desolate wilderness: yea, and nothing shall escape them.... The earth shall quake before them, the heavens shall tremble: the sun and the moon shall be dark, and the stars shall withdraw their shining."
FIG. 21.—LOCUST (Locusta Migratoria).
But it is kindly ordained that these visitations shall only occasionally take place, and even when they do, terrible as is the infliction, a benefit in reality outweighing the injury often succeeds; for the land in these countries is often made almost barren by the quantities of tangled roots and stubble on the surface of the earth, which by the destructive powers of these insects is completely removed, and their manure left in its place, so that the fertility of the ground is much increased (often tenfold) after their visits.
The thousands of species of insects which exist, render it impossible in a work like this, even to name them, but under the separate orders will be given a slight outline of the more important.
FIG. 22.—THE STAG BEETLE (Lucanus cervus).
Insects are divided, according to the character of their wings, into nine orders.
1. Coleoptera (Black-winged).
The Coleoptera are those insects generally denominated Beetles, they have four wings, the two outer of which are not used to fly with, but as cases to cover and protect the other two; they are called "elytra," are horny and firm in texture, and in some cases, as the Diamond Beetle and Musk Beetle, beautifully ornamented; the under pair of wings fold transversely so as to pack up under the outer ones, which are shorter. All Beetles live but one season, both sexes die before winter, leaving nothing but their eggs to continue the species, the larvæ which come from these are very destructive, eating most voraciously; for the most part, Beetles feed on decaying substances such as dung, &c., and are therefore useful creatures; there are between 40,000 and 50,000 species of them. Beetles have been called the scavengers of nature, and truly they are so, for they (with other insects) clear off all dead matter, whether animal or vegetable; the Geotrupes stercorarius, and others, dig holes in the ground and bury the excrement which is deposited on the surface, thus doing a great service to vegetation, taking it down to nourish the roots of the grass and other plants instead of allowing it to harden and decompose on the surface. All dead animals are at once attacked and devoured by insects, and the Beetles play their full share in this necessary operation.
There are certain Beetles, called Burying Beetles (Necrophorus vespillo), which remove the earth from under the dead bodies of small animals, such as birds or mice, till they are beneath the level of the ground, when they cover them up and deposit their eggs in them; these bodies form stores of food for the future larvæ.
The Stag Beetle (Lucanus cervus, fig. 22), the Dor Beetle (Geotrupes stercorarius), the Cockchaffer (Melolontha vulgaris), the Musk Beetle (Cerambyx moschatus, fig. 16), and the Lady-bird (Coccinella), are well-known members of this order.
2. Orthoptera (Straight-winged).
The Orthoptera are those insects whose wings fold longitudinally; they have two pairs, but the anterior pair are horny and serve as wing-cases to the posterior pair; their food is chiefly vegetable, but to many of their species any kind is acceptable, as their mouths are suitable for grinding-up hard substances. The Locusts (Locustidæ, fig. 21), Grasshoppers (Gryllidæ), Crickets (Achetidæ, fig. 16), and Cockroaches (Blattidæ), or Black-beetles, as they are sometimes incorrectly called, belong to this tribe. Their metamorphoses are not so complete as in many other insects, for they never entirely change their form; the larva as it leaves the egg has no wings, but otherwise is much like the parent; it changes its skin several times, which stage is analogous to the pupa state, after casting it five times and obtaining wings, it becomes the imago or perfect insect. The ravages of the Locusts are so well known that little need be said; the following is from Kirby and Spence's Entomology:—
"Although this animal be not very tremendous for its size, nor very terrific in its appearance, it is the very same whose ravages have been the theme of naturalists and historians in all ages, and upon a close examination you will find it to be peculiarly fitted and furnished for the execution of its office. It is armed with two pairs of very strong jaws, the upper terminating in short, and the lower in long teeth, by which it can both lacerate and grind its food; its stomach is of extraordinary capacity and powers; its hind legs enable it to leap to a considerable distance, and its ample vans are calculated to catch the wind as sails, and so to carry it sometimes over the sea; and although a single individual can effect but little evil, yet when the entire surface of a country is covered by them, and every one makes bare the spot on which it stands, the mischief produced may be as infinite as their numbers. So well do the Arabians know their power, that they make a Locust say to Mahomet, 'We are the army of the Great God; we produce ninety-nine eggs; if the hundred were completed, we should consume the whole earth and all that is in it.'"
3. Neuroptera (Nerve-winged).
The Neuroptera comprise the Dragon-fly (Libellulina, fig. 16), Ant-lion (Myrmelion), Caddis-flies (Phryganidæ), and the May-flies (Ephemera); these insects have wings of a beautiful network structure, as may be seen in the Dragon-fly, they make their appearance about the middle of June in the locality of ditches and ponds. The Caddis-fly is noted for the peculiar case which the larva makes for itself; the larva inhabits the water and the ease is made of little fragments of wood, shell, and sand, agglutinated together so as to float; the perfect insect is not aquatic, and flies away when formed. The May-flies are noted for the shortness of their existence, the larvæ live in the water, and many of them are eaten by fishes who are very fond of them, but sufficient numbers come to the perfect state, to form complete clouds in the air where the larvæ were, these creatures live but a day, and some of their species but an hour or two, in the perfect state, they deposit their eggs in the water, which come to life in the mud at the bottom. The flight of these fragile beings and their short-lived holiday festivities are well described by Kirby and Spence:—
"In the beginning of September, for two successive years, I was so fortunate as to witness a spectacle of this kind, which afforded me a more sublime gratification than any work or exhibition of art has power to communicate. The first was in 1811. Taking an evening walk near my house, when the sun, declining fast towards the horizon, shone forth without a cloud, the whole atmosphere over and near the stream swarmed with infinite myriads of Ephemeræ and little gnats of the genus chironomus, which in the sun-beam appeared as numerous and more lucid than the drops of rain, as if the heavens were showering down brilliant gems. Afterwards, in the following year, one Sunday, a little before sunset, I was enjoying a stroll with a friend at a greater distance from the river, when in a field by the road-side the same pleasing scene was renewed, but in a style of still greater magnificence; for, from some cause in the atmosphere, the insects at a distance looked much larger than they really were. The choral dances consisted principally of Ephemeræ, but there were also some chironomi, the former, however, being most conspicuous, attracted our chief attention. Alternately rising and falling, in the full beam they appeared so transparent and glorious, that they scarcely resembled anything material; they reminded us of angels and glorified spirits drinking life and joy in the effulgence of the Divine favour. The Bard of Twickenham, from the terms in which his beautiful description of his sylphs is conceived in the 'Rape of the Lock' seems to have witnessed the pleasing scene here described:—
'Some to the sun their insect wings unfold,
Waft on the breeze, or sink in clouds of gold;
Transparent forms, too fine for mortal sight,
Their fluid bodies half dissolved in light;
Loose to the wind their airy garments flew,
Thin glittering textures of the filmy dew,
Dipt in the richest tincture of the skies,
Where light disports in ever mingling dyes,
While every beam new transient colours flings,
Colours that change whene'er they wave their wings.'"
4. Hymenoptera (Membrane-winged).
The Hymenoptera are those insects which have four membraneous wings. The Bees (Apidæ, fig. 16), Wasps (Vespidæ), the Ants (Formicidæ), and the Ichneumon Flies (Ichneumonidæ), are the chief tribes of this order. The Bees, Wasps, and Ants are celebrated for forming societies, more perfectly arranged and governed than in any other creatures but man. It is curious that the most perfect instincts (such as approach so nearly to reason that they almost defy us to make a distinction) should have been given by the Creator to creatures so far removed from man in the scale of existence, and so little resembling him in any other particular. This is one of the stumbling-blocks in the way of those who wish to have it believed that all animals are progressive from certain types, which cannot be got over; if such were the case, man would be most nearly imitated by the Apes, and these again by those most nearly allied to them, and so on downwards, but here we find a government almost as perfect as that of the human species—an arrangement of work, a division of labour, buildings, storehouses, &c.—showing nearly all the social habits and feelings of man, in creatures who in form and size have no resemblance to him.
Kirby and Spence, in describing the societies of insects, say:—"But when we consider the object of these societies, the preservation and multiplication of the species, and the means by which that object is attained (the united labours and co-operation of perhaps millions of individuals), it seems as if they were impelled by passions very similar to those main-springs of human associations which I have just enumerated. Desire appears to stimulate them, love to allure them, fear to alarm them. They want a habitation to reside in and food for their subsistence. Does not this look as if desire were the operating cause which induces them to unite their labours to construct the one and provide the other? Their nest contains a numerous family of helpless brood. Does not love here seem to urge them to exemplary and fond attention, and those unremitted and indefatigable exertions manifested by the whole community for the benefit of these dear objects? Is it not also evident by their general and singular attachment to their families, by their mutual caresses, by their feeding each other, by their sympathy with suffering individuals and endeavours to relieve them, by their readiness to help those that are in difficulty, and finally by their sports and assemblies for relaxation? That fear produces its influences upon them seems no less evident, when we see them agitated by the approach of enemies, endeavour to repel their attacks, and to construct works of defence. They appear to have besides a common language, for they possess the faculty, by significative gestures and sounds, of communicating their wants and ideas to each other."
Numerous works have been entirely devoted to the habits and instincts of Bees and Ants, and very interesting they are, but it would be impossible to give an intelligible account of them in the small space allotted in this volume.
The wax of which Bees build their beautiful six-sided cells, and which is the whole source of all the wax used by men for a variety of purposes, is secreted in little scales or flakes, between the joints of the abdomen, from whence the wax-making Bees take it to build the comb; the cells of the comb are filled with honey, which is obtained by the Bees (by means of the apparatus shown at fig. 23), from the nectaries of flowers in the form of nectar, and is converted into honey in the honey-bag of the Bee, from whence it is discharged into the cells. Bees also collect the pollen from the flowers they visit, this adheres to the hairs on the Bee, and is scraped and brushed off, and collected into two little lots, which the Bee carries on each hind leg, this pollen is made into bee-bread. By scattering the pollen, flowers are often fecundated, for there are many plants, the female flowers of which are separate from the males, and it is only by insects and the wind, that the females are fecundated, for the Bee, with the pollen adhering to every part, first visits one flower and then another in search of nectar.
FIG. 23.—HONEY-LAPPING APPARATUS OF WILD SEA-BEE (Halictus), (a, magnified; a b, more highly magnified).
FIG. 24.—WHITE ANTS (1, Winged Female; 2, Female, distended with eggs).
FIG. 25.—NESTS OF WHITE ANTS.
With respect to the Ants, Kirby and Spence give the following account of the building of their habitations.
"The nest of Formica brunnea is composed wholly of earth, and consists of a great number of stories, sometimes not fewer than forty, twenty below the level of the soil, and as many above, which last, following the slope of the ant-hill, are concentric. Each story, separately examined, exhibits cavities in the shape of saloons, narrower apartments, and long galleries which preserve the communication between both. The arched roofs of the most spacious rooms are supported by very thin walls, or occasionally by small pillars and true buttresses; some having only one entrance from above, others a second, communicating with the lower story; the main galleries, of which, in some places, several meet in one large saloon, communicate with other subterranean passages, which are often carried to the distance of several feet from the hill. These insects work chiefly after sunset. In building their nest they employ soft clay only, scraped from its bottom when sufficiently moistened by a shower, which, far from injuring, consolidates and strengthens their architecture. Different labourers convey small masses of this ductile material between their mandibles, and with the same instrument they spread and mould it to their will, the antennæ accompanying every movement. They render all firm by pressing the surface lightly with their fore feet; and however numerous the distinct masses of clay composing these walls, and though connected by no glutinous material, they appear when finished, one single layer, well united, consolidated and smoothed. Having traced the plan of their structure, by placing here and there the foundations of the pillars and partition-walls, they add successively new portions; and when the walls of a gallery or apartment, which are half a line thick, are elevated about half an inch in height, they join them by springing a flattish arch or roof from one side to the other. Nothing can be a more interesting spectacle than one of these cities while building. In one place vertical walls form the outline, which communicate with different corridors by openings made in the masonry; in another we see a true saloon, whose vaults are supported by numerous pillars; and further on are the cross-ways or squares where several streets meet, and whose roofs, though often more than two inches across, the Ants are under no difficulty in constructing, beginning the sides of the arch in the angle formed by two walls, and extending them by successive layers of clay till they meet; while crowds of masons arrive from all parts with their particles of mortar, and work with a regularity, harmony, and activity, which can never enough be admired. So assiduous are they in their operations, that they will complete a story with all its saloons, vaulted roofs, partitions and galleries, in seven or eight hours. If they begin a story, and for want of moisture are unable to finish it, they pull down again all the crumbling apartments that are not covered in."
Every one has heard of the destructive as well as constructive qualities of the "White Ant;" another quotation from Kirby and Spence will illustrate both.
"When they find their way into houses or warehouses nothing less hard than metal or glass escapes their ravages; their favourite food, however, is wood of all kinds, except the Teak, and Ironwood, which are the only sorts known, that they will not touch; and so infinite are the multitudes of the assailants, and such is the excellence of their tools, that all the timber-work of a spacious apartment is often destroyed by them in a few nights. Exteriorly, however, everything appears as if untouched; for these wary depredators (and this is what constitutes the greatest singularity of their history) carry on all their operations by sap and mine, destroying utterly the inside of solid substances, and scarcely ever attacking their outside until they have first concealed it and their operations with a coating of clay. A general similarity runs through the proceedings of the whole tribe, but the large African species, called by Smeathman Termes bellicosus, is the most formidable. These insects live in large clay nests, from whence they excavate tunnels all round, often to the extent of several hundred feet; from these they will descend a considerable depth below the foundation of a house, and rise again through the floors; or, boring through the posts and supports of the building, enter the roof and construct their galleries in various directions.
"If a post be a convenient path to the roof, or has any weight to support, (how they discover it is not easily conjectured), they will fill it with their mortar, leaving only a track-way for themselves, and thus, as it were, convert it from wood into stone as hard as many kinds of freestone. In this manner they soon destroy houses, and sometimes whole villages, when deserted by their inhabitants, so that in two or three years not a vestige of them will remain. These insidious insects are not less expeditious in destroying the wainscoating, shelves, and other fixtures of a house, than the house itself; with the most consummate art and skill they eat away the inside of what they attack, except a few fibres here and there, which exactly suffice to keep the two sides, or top and bottom, connected, so as to retain the appearance of solidity after the reality is gone; and all the while they carefully avoid perforating the surface, unless a book or any other thing that tempts them should be standing upon it.
"Kœmpfer, speaking of the White Ants of Japan, gives a remarkable instance of the rapidity with which these miners proceed. Upon rising one morning he observed that one of their galleries of the thickness of his little finger had been formed across his table; and upon a further examination he found that they had bored a passage of that thickness up one foot of the table, formed a gallery across it, and then pierced down another foot into the floor; all this was done in the few hours that intervened between his retiring to rest and his rising."
Most of this order are armed with some weapon of defence. The Bee and Wasp have each a most formidable sting, with which they are able to inflict a wound fatal to most insects. The Ants have a peculiar secretion, consisting of formic acid, which they eject with great force, and which has a very disagreeable smell. The eggs of Ants when hatched produce a small grub, which spins itself a sort of cocoon, and in this state it so much resembles a grain of corn, that it has been mistaken for it; this error has given rise to the supposition that Ants store up corn for winter, whereas they never eat corn, but the care they take of these larvæ, removing them from place to place, taking them up in their mandibles and running along with them, has been mistaken for the act of storing away grains of corn.
5. Strepsiptera (Twisted-winged).
This order includes but a few species; Dr. Baird in his Cyclopædia, gives the following account of them:—
"Certain insects were discovered by Kirby, living parasitic in the abdomen of some Andrenæ, which at that time were nondescript, and could not be referred to any existing order. They were afterwards placed in an order by themselves, which he called Strepsiptera. The larvæ live in the bodies of Bees, Wasps &c., and the males only undergo a perfect metamorphosis; the females, even when adult, have neither legs, wings, nor eyes, but resemble larvæ, and continue to live parasitic in the bodies of the Hymenopterous insects within which they were born. The characters are thus taken from the male and consist chiefly in the structure of the wings. The anterior pair are quite rudimentary, being transformed into a pair of short, slender, contorted appendages resembling narrow balancers or halters. The posterior pair are large and membraneous, their nervures are only longitudinal, so that they are able to fold them like a fan. They have large globular eyes, with the facets few, but of comparatively large size."
FIG. 26.—STYLOPS ANDRENÆ.
"About ten or twelve species are known, forming a small family, "Stylopidæ." The genus Stylops may be taken as the type, and contain such species as have the tarsi with four points and the antennæ with six."
6. Lepidoptera (Scaly-winged).
This order includes the Butterflies and Moths, they have four wings, which are large and covered with minute scales, which are for the most part of a heart or battledore shape, as in fig. 27. The wings of these insects are many of them beautifully marked and tinged. There are about 12,000 species, by some divided into "diurnal" (or those which fly by day), "crepuscular" (or those which fly in the evening), and "nocturnal" (or those flying by night). The Moths are mostly crepuscular and nocturnal, while the Butterflies are chiefly diurnal, but the most usual distinction between the Moth and Butterfly consists in the form of the antennæ, those of the Moth being feather-shaped, while those of the Butterfly have a small knob at the end, or, as it is called, "club-shaped." The Lepidoptera feed upon the nectar of flowers, for which purpose they are furnished with a long proboscis or "Haustellium," which is curled up under the head, it consists of two semi-cylindrical pieces which when placed side by side form a tube, up which the nectar is drawn by capillary attraction. The metamorphosis of these insects is complete.
FIG. 27.—SCALES FROM MOTH'S WING
(Magnified).
The Silkworm (Bombyx mori) belongs to this order. It is the most important of all insects to man, as from it alone all the silk of commerce is obtained. Its cocoon is of a beautiful yellow colour, varying in shade from orange to pale straw-colour; the silk of one cocoon weighs somewhere about three grains; it would therefore, at this calculation, take 1920 worms to spin one pound. The annual import of silk into this country alone is about 7,000,000 pounds, it must therefore take 13,440,000,000 Silkworms to supply us with silk yearly! The Silkworm feeds almost exclusively on the leaves of the mulberry.
FIG. 28.—THE SILKWORM (Bombyx mori).
1, the Eggs; 2, the young Silkworms; 3, the full-grown Silkworm; 4, the Cocoon; 5, the Chrysalis; 6, the Moth.
7. Hemiptera (Half-winged).
The Hemiptera have two pairs of wings, the hindermost small, and the foremost pair half horny and half membraneous, the base being horny, and the apex membraneous. They include the Bugs, some of which are aquatic, as the Water Scorpion (Nepa), and the Water Boatman (Natonecta), which swims on its back, rowing itself by means of a pair of long legs, which look like oars; the common bed Bug is also of this order, although wingless, as are also the Plant Lice (Aphides), which, however, obtain wings in their perfect state.
8. Diptera (Two-winged).
FIG. 29.—PART OF GNAT'S WING, MAGNIFIED.
The Diptera include the common House Fly (fig. 16), Bluebottle Fly, Gnat, and many others; their wings are like the Neuroptera, but they have but one pair, the other pair being undeveloped, form little knobs called "balancers." The wings of Flies are generally covered with short stout hairs, as seen in fig. 29; the common Fly feeds upon almost anything, but some of the Diptera feed exclusively on the blood of other animals; the Gnat (Culex pipiens), of which the Mosquito is a variety, deposits its egg in the water on any floating substance, the larva which comes from the egg is aquatic, living with its head downwards, the end of the abdomen only being above the water, in this there is a spiracle or breathing orifice, which enables it to take in the air; the Gnat, when it comes from this larva, stands on its shell for a moment, and then flies off, for it is not suited to live in the water; this history of the early stages of its life, accounts for Gnats being always found in such numbers near pools of water. The Tsetse, which Dr. Livingstone describes as being so fatal to cattle, is of this order; he says, "It is well known that the bite of this poisonous insect is certain death to ox, horse, or dog.... A most remarkable feature in the bite of the Tsetse is its perfect harmlessness to man and wild animals, and even calves, so long as they continue to suck the cows."
9. Aptera (Wingless).
FIG. 30.—FLEA (Pulex irritans) MAGNIFIED.
To this order belongs the Flea (Pulex irritans), which is furnished with lancet-shaped weapons, through which it sucks the blood of other animals, for it is entirely parasitic, and also the "Chigeo" (Pulex penetrans), which is a troublesome and even dangerous pest in the West Indies; it penetrates the skin of the feet, and deposits its young beneath it.
FIG. 31.—ARACHNIDA. 1, Spider (Epeira Diadema); 2, Scorpion (Scorpio).
FIG. 32.—LONG-LEGGED HOUSE-SPIDER (Aranæ domestica).
The last class of the Articulata, the Arachnida, includes the Spiders, Scorpions, Centipedes, and Millipedes. The Arachnida differ from insects, in having eight or more legs, more than two eyes, no wings, and no head; the Spiders have four pairs of legs, and six, eight, or more, simple eyes, which appear as minute spots on the upper part of the thorax. Spiders nearly all live by preying upon small insects, which they catch in several ways, but by far the most general mode is by constructing a web or net to entangle them; the threads of this web are made of a fluid glutinous substance, which is secreted within the abdomen, and which they project from extremely minute orifices, several of which exist on the point of little projections called "spinnarets," this liquid dries into a solid thread immediately it comes into contact with the air; it is extremely strong, and so fine that several thousand of the single fibres will only make the size of a human hair. The Garden Spider (Epeira diadema) is often called the Geometrical Spider, from the regularity of its web. These Spiders will often place a thread from one spot to another, where it would seem impossible that they could attach it, such as from the branch of a tree to the corner of a house twenty feet or more from the ground; it has never been accurately determined how the Spider does this, and it is the more difficult to observe, as it is always done in the night, but it has been supposed that a fine thread is spun, and that the wind carries it across, when it is strengthened and afterwards made tight. The Spider (Araneæ domestica) that makes "cobwebs" in the corners of rooms, is called the Weaving Spider. Some Spiders are called Hunting Spiders, they do not construct webs, but pounce upon their prey with a leap; the Mygale avicularis of South America is one of this kind; it is said that some grow so large that their feet spread out a foot wide. The Long-legged Spider, often found in our houses, and of which fig. 32 is an exact copy, measures 3½ inches, and is the largest species we have. There are also aquatic Spiders, which feed upon insects in the water and dive down for them; their surface being hairy and unctuous, retains sufficient air to bring them up and prevent them being wetted. The eyes of Spiders are different from those of other insects; they appear as simple, shining spots, or "ocelli," and not compound eyes, having a great many "ocelli" compounded into one. These "ocelli" are arranged in a group of eight or more, and placed on the upper part of the thorax, for Spiders have no head, although generally represented with one. The eggs of Spiders are generally deposited in some sheltered place, fastened together and partly covered with a net-work of a sort of yellow silk, very much resembling the cocoon of the Silkworm. The Scorpion, so terrible in appearance, and in its sting so deadly, and which is sometimes a foot in length, belongs to this order. It has eight legs, and a pair of claws like a lobster, the body is lengthened into a sort of tail, at the end of which is a claw or sting, like the poison fang of a serpent, with a poison bag at its root; its effects are often fatal to man, and always so to the insects and other small animals upon which the Scorpion feeds, its usual mode of killing which, is to catch them with its claws and then to sting them to death. The Centipede is a scarcely less frightful creature; in South America and the West Indies it is sometimes found to grow to eight or ten inches in length, it is of a long jointed form, with generally twenty-one pairs of legs, although some have double this number; its bite is much to be dreaded, as it is poisonous, especially the "Scolopendræ," which have a poison gland, like the snake; in this country they are very small indeed, and are generally found in moist places.
The Centipedes and Millipedes are, by some, placed in the class Arachnida, but by others in a separate class called "Myriopoda," divided into two orders, the Chilognatha, which have rounded cylindrical bodies, and generally more than one pair of legs to each segment of the body, and the Chilopoda, which have a distinct flattened head and but one pair of legs to each segment.
FIG. 33.—MOLLUSCA.
1, Nautilus (Argonauta); 2, Clio Borealis; 3, Mussel (Mytilus edule).
The last of the three great divisions of the Invertebrata is formed by the Mollusca; it is divided into six classes, (see [page 218]). The Mollusca are characterised by having no internal skeleton, nor external horny case, as in the Articulata; they are rather soft, and either void of solid covering, or possessed of "shells" composed chiefly of earthy matter (chalk), and in one or two pieces, called valves, hence the names, uni-valve and bi-valve; all shells of this description belong to the Mollusca, some of which have no means of locomotion, as Oysters; others have a "foot" covered with a muscular expansion, called the "mantle," by which they glide onwards, as the Snail.
1. The Tunicata have no shell or hard covering, but are of a pretty firm consistence; they are either fixed to rocks and sea-weeds, or float about freely, and are either solitary, social, or compound. The "Ascidians" are united in groups, and are all connected by a common stalk or "Stolon," from which they grow by buds.
2. The Brachiopoda. These Molluscs are furnished with a pair of shells, within which the animal lives; one of these shells (the ventral one) has a small hole in it, close to the hinge, and through this a long tendinous cord passes, which fixes the creature to some stone or rock, hence the name Brachiopodous, which means arm-footed. The young of this Mollusc are not fixed, but float about. The Lingula has horny shells, and the foot passes out between them; these creatures were some of the first created, if not the very first; the shells of Terebratula are found in vast quantities in the oldest fossiliferous strata.
FIG. 34.—COCKLE (Cardium edule).
3. The Lamellibranchiata include a great many of our most ordinary Mollusca, commonly known as "shell fish." They have a pair of shells, and are thence called "bivalve." The Oyster (Ostrea edulis), Mussel (Mytilus edulis), Cockle (Cardium edule), Scallop (Pecten), belong to this class. Oysters form a considerable article of commerce, thirty or forty thousand bushels are brought each season to London; they are dredged up from "beds," where they are found in great quantities. They spawn in May and June, and are not then good. There is an old and a well-known saying, that "Oysters are not fit to eat, unless there is an R in the month," all the names of the months containing an R but May, June, July, and August. The spawn is collected and placed in artificial beds, consisting of shallow places or hollows in the sea, where the tide will not wash them away, and whence they can be easily removed when sufficiently grown, which is in five or six years; these creatures have no powers of locomotion, but remain where the tide washes them; but Scallops, Cockles (fig. 34), and Mussels (fig. 33), have the power of fixing themselves to any substance they wish, by means of the "byssus" or beard, which is a tuft of fibres passing out from between the shells; and it is said, the Scallops have the power of progression, by suddenly opening and shutting the shells.
4. The Pteropoda are Mollusca which have no shell, or a very thin one; the Clio borealis (fig. 33), which forms the chief food of the Whale, is found in great multitudes in the Arctic seas, it swims about by means of two extensions, similar to wings. The Hyalœa has a small round transparent shell.
FIG. 35.—SNAIL (Helix aspersa), AND SLUG (Limax cinerius).
FIG. 36.—WENTLE-TRAP SHELL
(Scalaria).
5. The Gasteropoda are extremely numerous; most of them have univalve shells, but many of them have none, as the Garden Slug (Limax, fig. 35). The Whelk (Buccinum undatum), Perriwinkle (Littorina littoria), Garden Snail (Helix aspersa, fig. 35), and the Wentle-trap (Scalaria, fig. 36), are the most familiar examples of this class. These Mollusca walk by means of the mantle, which is muscular, and capable of alternate contraction and expansion; they breathe by means of lungs on their back beneath the shell, and to which there is an opening in their side. What are usually called the horns are four in number, two short and two long; they are tentaculæ, but what is peculiar in them is the circumstance of having the eyes placed at their ends. These Mollusca have a sort of valve, which, when they retire into the shell, closes it like a lid; it is called the "Operculum;" in some cases it is horny, as in the Perriwinkle, and in others, resembles shell; the shells of these mollusca are coiled into a spiral, this is caused by the shell always growing by additions to the edges of the mouth, and in nearly every case this spiral turns in the same direction that a screw does, but in a very few it turns in the opposite direction, as in the "Fusus contrarius."
6. The Cephalopoda include the "Cuttle-Fish," and Nautilus (fig. 33). They are furnished with eight or ten tentacula or arms, which spring from the head, and which are covered with suckers; the mouth is in the centre, and these tentacula are used to lay hold of their prey and convey it to the mouth; they have two perfect eyes, and they breathe by gills. The Nautilus has a univalve shell, which is of a very graceful and elegant form; its interior is divided into chambers, with a syphon running through them, by which the air is exhausted or compressed so as to cause them to sink or swim; the animal occupies only the outer chamber; the extinct Ammonite belonged to this class. It is from the Cuttle-Fish (Sepiæ) that the beautiful dark brown pigment, known as "sepia," is obtained, and also the material of which Indian-ink is made.