Outlines of Creation

by Elisha Noyce

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.