to the molecules. Both, however, he asserts, have a propensity or appetency to form or create, and "they reciprocally stimulate and embrace each other and instantly coalesce; and may thus popularly be compared to the double affinities of chymistry."

Subtile as these hypotheses are, they are open to forcible objections of which a few only will suffice. The notion of this occult force is identical with that, which, we shall see hereafter, has prevailed as regards life in general and leaves the subject in the same obscurity as ever. What do the terms plastic, cosmic, or vegetative force, or Bildungstrieb express, which is not equally conveyed by vital force,—that mysterious property, on which so many unfathomable processes of the animal body are dependentand of the nature or essence of which we know absolutely nothing? The objection, urged against the doctrine of Hippocrates,—that we have no evidence of the existence of female sperm, applies equally to the hypotheses that have been founded upon it; and even were we to grant, that the ovarium is a receptacle for female sperm, the idea, that such sperm is constituted of organic molecules, derived from every part of the body, is entirely gratuitous. We have no facts to demonstrate the affirmative; whilst there are many circumstances, that favour the negative. The individual, for example, who has lost some part of his person—nose, eye or ear, or has had a limb amputated, still begets perfect children; yet whence can the molecules, in such cases, have been obtained? It is true that if the mutilation affect but one parent, the organic molecules of the lost part may still exist in the seed of the other; but we ought, at least, to expect the part to be less perfectly formed in the embryo, which it is not. Where two docked horses are made to engender, the result ought, a fortiori, to be imperfect, as the organic molecules of the tail could not be furnished by either parent, yet we find the colt, in such cases, perfect in this appendage. An elucidative case is also afforded by the fœtus. If we admit the possibility of organic molecules constituting those parts that exist in the parents, how can we account for the formation of such as are peculiar to fœtal existence. Whence are the organic molecules of the navel-string, or of the umbilical vein, or of the ductus venosus, or the ductus arteriosus, or the umbilical arteries, all of which have to be described hereafter, -obtained?

These and other objections have led to the abandonment of the theory of Buffon, which remains merely as a monument of the author's ingenuity and elevation of fancy.

2. Evolution. According to this theory the new individual pre-exists in some shape in one of the sexes, but requires to be vivified by the other, in the act of generation; after which it commences the series of developments or evolutions, which lead to the formation of an independent being.

The great differences of sentiment, that have prevailed under VOL. II.

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this view, have been owing to the part which each sex has been considered to play in the function. Some have considered the germ to exist in the ovary, and to require the vivifying influence of the male sperm to cause its evolution. Others have conceived the male sperm to contain the rudiments of the new being, and the female to afford it merely a nidus, and pabulum during its development. The former class of physiologists have been called ovarists;—the latter spermatists, seminists, and animalculists.

The ovarists maintain, that the part furnished by the female is an ovum from the ovary; and this ovum they conceive formed of an embryo and of particular organs for the nutrition and first development of the embryo; and adapted for becoming, after a series of changes or evolutions, a being similar to the one whence it has emanated. The hypothesis was suggested by the fact, that in many animals but a single individual is necessary for reproduction; and it is easier, perhaps, to consider this individual female than male; as well as by what is noticed in many oviparous animals. In these the part, furnished by the female, is manifestly an ovum or egg; and in many, such egg is laid before the union of the sexes, and is fecundated, as we have seen, externally. By analogy, the inference was drawn, that this may happen to the viviparous animal also.

The notion is said, but erroneously, to have been first of all advanced by Joseph de Aromatariis, in his Epistola de generatione plantarum ex seminibus, published at Venice, in 1625. It was developed by Harvey, who strenuously maintained the doctrine omne vivum ex ovo. The anatomical examinations of SYLVIUS, VESALIUS, FALLOPIUS, DE GRAAF, MALPIGHI, VALLISNIERI and others,—by showing, that what had been previously regarded as female testes, and had been so called, were organs containing minute vesicles or ova, and hence termed, by Steno, ovaria,—were strong confirmations of this view, and startling objections to the ancient theory of epigenesis, and the problem appeared to be demonstrated, when it was discovered, that the vesicle or ovum leaves the ovarium and passes through the Fallopian tube to the uterus.

The chief arguments, that have been adduced in favour of this doctrine are:—First. The difficulty of conceiving the formation, ab origine, of an organized body, as no one part can exist without the simultaneous existence of others. Secondly. The existence of the germ prior to fecundation in many living beings. In plants, for example, the grain exists in a rudimental state in the flower, before the pollen, which has to fecundate it, has attained maturity. In birds, too, the egg must pre-exist, as we find that those, which have never had intercourse with the male, can yet lay. This is more strikingly manifest in many fishes, and in the batracia or frog kind; where the egg is not fecundated until after extrusion. Spallanzani, moreover, asserts, that he could distinguish the pre

sence of the tadpole in the unfecundated ova of the frog; and HALLER that of the chick in the infecund egg; at least he has seen them containing the yolk, which, in his view, is but a dependence of the intestine of the foetus, and if the yolk exists the chick exists also. Thirdly. The fact, before referred to, that, in certain animals, a single copulation is capable of fecundating several successive generations. In these cases, it is argued, the germs of the different generations must have existed in the first. Fourthly. The fact of natural and accidental encasings or embôitements; as in the bulb of the hyacinth, in which the rudiments of the flower are distinguishable; in the buds of trees, in which the branches, leaves, and flowers, have been detected in miniature, and greatly convoluted; in the jaws of certain animals, in which the germs of different series of teeth can be detected; in the volvox, a transparent animal, which exhibits several young ones encased in each other; in the common egg, which occasionally has another within it; and in the instances on record, in which human fœtuses have been found in the bodies of youths, of which there is a striking example in the Museum of the Royal College of Surgeons of London; and a similar case in a boy, fourteen years of age, has been related by Dupuytren. Fifthly. The fact of the various metamorphoses, that take place in certain animals. Of these we have the most familiar instances in the batracia and in insects. The forms they have successively to assume are evidently encased. In the chrysalis, the outlines of the form of the future butterfly are apparent; and in the larva we observe those of the chrysalis. The frog is also apparent under the skin of the tadpole. Sixthly. The fact of artificial fecundation, which has been regarded, by the ovarists, as one of the strongest proofs of their theory; the quantity of sperm employed, as in the experiments of Spallanzani, already detailed, being too small, in their opinion, to assist in the formation of the new individual, except as a vivifying material. Lastly. They invoke the circumstance of partial reproductions, of which all living bodies afford more or less manifest examples; as the reproduction of the hair and nails in man; of the teeth in the rodentia; of the tail in the lizard; of the claw in the lobster; the head in the snail, &c. &c. All these phenomena are, according to them, owing to each part possessing within itself germs destined for its reproduction, and requiring only favourable circumstances for their development. The partisans of the doctrine of epigenesis, however, consider these last facts as opposed to the views of the ovarists; and they maintain that in such cases there is throughout a fresh formation.

The chief objections, that have been urged against the hypothesis of the ovarists, are:—First. The resemblance of the child to the father a subject which we shall refer to presently. The ovarists cannot of course deny that such resemblance exists; and they ascribe it to the modifying influence exerted by the male sperm,

but without being able to explain the nature of such influence. They affirm, however, that the likeness of the mother is more frequent and evident. Certain cases of resemblance, it must be admitted, are weighty stumbling-blocks to ovism, or to the doctrine of a pre-existent germ in the female. It is a well known fact, that six-fingered men will beget six-fingered children. How can we explain this upon the principle of the pre-existence of the germ in the female, and of the part played by the male sperm being simply that of a vivificative agent; and must we suppose, in the case of monstrosities, that such germs have been originally monstrous? Secondly. The production of hybrids is one of the strongest counter-arguments. They are produced by the union of the males and females of different species. Of these the mule is the most familiar instance the product of the ass and the mare. This strikingly participates of the qualities of both parents, and, consequently, the pre-existing germ in the female must have been more than vivified by the sexual intercourse. Its structure must have been altogether changed, and all the germs of its future offspring annihilated, as the mule is seldom fertile.

If a white woman marries a negro, the child is a mulatto; and if the successive generations of this woman are continually united to negroes, the progeny will ultimately become entirely black; or at least the white admixture will escape recognition. As a general principle, the offspring of different races have an intermediate tint between those of the parents; and the proportions of white and black blood, in different admixtures, have even been subjected to calculation, in those countries where negroes are common. The following table represents these proportions, according to the principles sanctioned by custom.

The two last are considered to be respectively white and black; and of these the former are white by law and consequently free in the British West India Islands. All these cases exhibit the great influence, exerted by the father upon the character of the offspring, and are great difficulties in the way of supposing, that the male sperm is simply a vivifier of the germ pre-existing in the female. Thirdly. The doctrine of the ovarists does not account for the greater degree of fertility of cultivated plants and of domesticated

animals. Fourthly. The changes, induced by the succession of ages on the animal and vegetable species inhabiting the surface of the globe, have been adduced against this hypothesis.

In examining the geological character of the various strata that compose the earth, it has been observed by geologists, that many of these contain imbedded the fossil remains of animals and vegetables. Now, under the supposition, that those rocks on which others rest are the oldest, and that the successive strata above these are more and more modern, it has been found, that the organic fossil remains in the different strata differ more and more from the present inhabitants of the surface of the globe in proportion to the depth we descend; and that the remains of those beings, that have always been the companions of man, are found only in the most recent of the alluvial deposites,—in the upper crust of the earth.

In the older rocks the impressions are chiefly of the less perfect plants as the ferns and reeds; and of the lower animals—the remains of shells and corals; whilst fish are uncommon. In the more recent strata, the remains of reptiles, birds and quadrupeds are apparent; but all of them differ essentially from the existing kinds; and in none of the formations of more ancient date has the fossil human skeleton been met with. The pretended human bones, conveyed by Spallanzani from the Island of Cerigo—the ancient Cythera—are not those of the human species any more than the bones of the Homo diluvii testis of Scheuchzer; and the skeleton of the savage Galibi, conveyed from Gaudaloupe and deposited in the British museum is imbedded in a calcareous earth of modern formation. From these facts it has been concluded, that man is of a date posterior to animals in all countries where fossil bones have been discovered.

These singular facts, furnished by modern geological inquiry, have been attempted to be explained by the supposition, that the present races of animals are the descendants of those, whose remains are met with in the rocks, and that their difference of character may have arisen from some change in the physical constitution of the atmosphere, or of the surface of the earth, producing a corresponding change on the forms of organized beings. It has been properly remarked, however, by Dr. Fleming, that the effect of circumstances on the appearance of living beings is circumscribed within certain limits, so that no transmutation of species was ever ascertained to have taken place; whilst the fossil species differ as much from the recent kinds, as the last do from each other; and he adds, that it remains for the abettors of the opinion to connect the extinct with the living races by ascertaining the intermediate links or transitions. This will probably ever be impracticable. The difference, indeed, between the extinct and the living races is in several cases so extreme, that many naturalists