The author of the Vestiges of Creation has put forth an hypothesis founded on the preceding conjectures, but more compact and conclusive. He is, as we have seen, in favour of the progressive change of species, adopting the notion that men once had tails, and that the rudiments of this condal appendage are found in an undeveloped state in the os coccygis (p. 199.) His leading idea of the progress of organic life is that the "simplest and most primitive type under a law to which that of like production is subordinate, gave birth to the type next above it; that this again produced the next higher, and so on to the very highest, the stages of advance being in all cases very small—namely, from one species only to another; so that the phenomenon has always been of a modest and simple character." (p. 231.) The arguments by which the author endeavours to prove his hypothesis may be thus compressed.
According to him foetal development is a science, illustrated by HUNTER'S great collection of the Royal College of Surgeons, and established by the conclusions of ST. HILAIRE and TIEDMANN. Its primary positions are—1. That the embryos of all animals are not distinguishably different from each other; and, 2. That those of all animals pass through a series of phases of development, each of which is the type or analogue of the permanent configuration of tribes inferior to it in the scale. Higher the order of animals, the more numerous its stages of progress. Man himself is not exempt from this law. His first foetal form is that which is permanent in the animalcule; it next passes through ulterior stages, resembling successively a fish, a reptile, a bird, and the lower mammalia before it attains its specific maturity. The period of gestation determines the species; protract it, and the species is advanced to a higher class. This might be done by the force of certain conditions operating upon the system of the mother. Give good conditions and the young she produces will improve in development; give bad conditions and it will recede. Cases of monstrous birth in the human species are appealed to, in which the most important organs are left imperfectly developed; the heart, for instance, having sometimes advanced no further than the three-chambered or reptile form, while there are instances of that organ being left in the two-chambered or fish-like form. These defects arise from a failure of the power of development in the mother, occasioned by misery or bad health, and they are but the converse of those conditions that carry on species to species. The differences of sexes is the result of foetal progress only one degree less marked than that of a change of species. Sex is fully ascertained to be a matter of development. All beings are at one stage of the embryotic progress female. A certain number of them are afterwards advanced to the more powerful sex. For proof of this, the economy of bees is cited; when they wish to raise a queen-bee, or true female, they prepare for the larva a more commodious cell, and feed it with delicate food. But we shall here stop to remark on the author's argument up to this point.
It is manifest, according to his hypothesis, that neither sex nor species depend on the ancestral germ, but simply on physical conditions and mechanical development. But eminent physiologists deny that the facts are such as he has stated; they deny, as we have stated in a former section, that the foetal progress is such as the Vestiges represent them to be; they deny that the human embryo, for example, exhibits in successive stages the form of fish, lizard, bird, beast: on the contrary, they contend that it is only in the earliest period of the organic germ, when the manifestations are almost too obscure for microscopic sense, that any resemblance exists; that immediately the organic germ becomes sensible to observation, sex and species are found to be fixed. Take, for example, the vertebrata; in these, by some mysterious bond of union, the organic globules are seen to arrange themselves into two nearly parallel rows. We may then say that the keel of the animal is laid down, and in it we have the first rudiments of a backbone and a continuous spinal chord. But during the progress and completion of this first organic process no changes have been observed assimilating the nascent embryo to any of the inferior animals. The next series of changes in the germinal membrane are of two kinds—in one the nervous system, the organs of motion, the intestinal canal, the heart and blood-vessels are manifested; the other set of changes, which are subsequent, produce the perfection of the animal and determine its sex. All these manifestations result from germinal appendages that cannot be severed or changed without ruin to the embryo, and the conditions essential to life as the structure advances are due temperature, due nutriment of the nervous organs, and due access to the atmospheric air. Without, therefore, pursuing further this part of the inquiry, we shall remark that the question at issue between the Vestiges and its opponents is one of facts—of conflicting evidence—to be tried by the jury of the public, or rather by those who, from science or professional pursuits, are competent to form an authoritative opinion. Our own conclusion is, that in face of the testimony adduced against it, the author's hypothesis is not yet established.
For proof that species do change, and that even new species have been actually and recently produced, the author has adduced statements certainly as questionable and little satisfactory as his representation of foetal phenomena. We can only briefly enumerate them. First we are told that oats sown at midsummer, if kept cropped down, so as to be prevented shooting into ear, and then allowed to remain in the ground over winter, will spring up next year in the form of rye (p. 226). This need not be disputed about; the experiment can be easily tried; but if rye were the result, it would be no conclusive proof of a translation of species. Perhaps the oat-plants perished under the operation of repeated cuttings, and the rye seed was dormant in the earth and sprung up in its place; or, if not so, oats and rye may not be different species, only varieties of the same species. They are scarcely more dissimilar than the primrose, the cowslip, and the oxlip, which have all been raised from the seed of the same plant, and are now regarded by botanists as varieties instead of species.
When lime is laid on waste ground we are told that white clover will spring up spontaneously, and in situations where no clover-seed could have been left dormant in the soil (p. 182). But how is this to be proved? It is certain that seeds will remain dormant in the soil for centuries, and then spring up the first year the soil is turned up by the plough. Some seeds have retained their vitality for thousands of years in the old tombs of Egypt; they have been repeatedly brought to England, sown, and produced good wheat.
We are next told that wild pigs never have the measles, they are produced by a hyatid and the result of domestication; that a tinea is found in dressed wool that does not exist in its unwashed state; that a certain insect disdains all food but chocolate, and that the larva of oinopota cellaris only lives in wine and beer. All these are articles manufactured by man, and are adduced as proofs of animal life, independent of any primordial egg. The entoza are dwelt upon; they are creatures living in the interior of other animals, of which the tape-worm that infests the human body is a melancholy instance. In these illustrations we think the author has some show of reason, for we feel convinced that there is such a thing as spontaneous generation from the inorganic substance, wisely provided for clearing the earth of noxious effluvia and putrid matter, and converting them into new elements conducive to health and life. We believe in this source of vitality from its wisdom and necessity, its necessity and wisdom, in our estimate, being strong presumptive proofs of its existence in harmony with the general forecast and economy of nature. Of the self-originating spring of life, some of the examples adduced by the author are proofs, and of which we have familiar illustrations in cheese-mites, maggots in carrion, and the green fly that breeds so profusely in weak and decaying vegetation; in all which by some inscrutable law the organic germ, without an antecedent, appears to evolve from the dead or putrifying mass for its riddance and transmutation.
Conceding, however, thus far to the author, we are not prepared to admit that the creative powers of Messrs. CROSSE and WEEKES has been established. These gentlemen are said (p. 190) to have introduced a stranger in the animal kingdom, a species of acarus or mite amidst a solution of silica submitted to the electric current. The insects produced by the action of a galvanic battery continued for eleven months are represented as minute and semi-transparent, and furnished with long bristles. One of the creatures resulting from this elaborate term of gestation was observed in the very act of emerging, in its first-born nudity, and sought concealment in a corner of the apparatus. Some of them were observed to go back into the parent fluid and occasionally they devoured each other; and soon after they were called to life, they were disposed to multiply their species in the common way! So much for the experiment; against its verity it is alleged, first, that the Acarus Crossii are not a new species, or if new, that neither Mr. CROSSE nor Mr. WEEKES, who repeated Mr. CROSSE'S experiment, produced them, but only aided by the voltaic battery the development of the insects from their eggs. Such a mode of generation is contrary to all human experience, and can only be believed in on the strongest corroborative proof.
Neither by chemistry nor galvanism can man, we apprehend, be more than instrumental and co-operative, not originally and independently creative. In almost every form of life, whether animal or vegetable, art can multiply varieties,—can train, direct—but cannot form new species. This is the mockery of science. With all its invention and resource, it cannot produce organic originals. It can rear a crab-apple into a golden-pippin, or wild sea-weed into a luxuriant cabbage; it can raise infinite varieties of roses, tulips, and pansies, but can create no new plant, fruit, or flower. Man can make a steam-engine, or a watch, but he cannot make a fly, a midge, or blade of grass. He is an ingenious compiler, but not a creator; and his powers of manufacture and conversion are restricted within narrow boundaries. He cannot wander far in the indulgence of his fancies without being recalled, and compelled to return to the first models set by the Great Architect. The further he strays from primitive types in the effort to improve, by crossing, cutting, and grafting, and proportionably less becomes the procreative force. Hybrids are notoriously sterile. Garden fruit is not permanent, and requires to be renewed from seed. The law seems universal in plants and animals, that the vital energy or germ is less forcible and prolific in the pampered and artificial, than in the natural and wild races.
HYPOTHESIS OF THE VITAL PRINCIPLE.
It is ascertained that the basis of all vegetable and animal substances consists in nucleated cells—that is, cells having granules within them. Nutriment is converted into these before being assimilated by the system. It has likewise been noted that the globules of the blood are reproduced by the expansion of contained granules; "they are, in short," says the Vestiges, "distinct organisms multiplied by the same fissiporous generation. So that all animated nature may be said to be based on this mode of origin; the fundamental form of organic being is a globule, having a new globule forming within itself, by which it is in time discharged, and which is again followed by another and another, in endless succession. It is of course obvious, that if these globules could be produced by any process from inorganic elements, we should be entitled to say that the fact of a transit from the inorganic to the organic had been witnessed." (p. 176.) "Globules," the author continues, "can be produced in albumen by electricity. If, therefore, these globules be identical with the cells which are now held to be reproductive, it might be said that the production of albumen by artificial means is the only step in the process wanting. This has not yet been effected." (p. 177.)