Thus, according to this opinion, man is the only type of animal life; and every inferior species is but an imitation, more or less perfect, of the same; an inchoation stopped in its course at a greater or shorter distance from the term to which the work of nature tends in its organization of the human embryo. In short, an [{72}] entoma in difetto, to use the language of Dante.
The doctrine is not new in the scientific world. It was proclaimed in the last century by Robinet, who held that all inferior beings are but so many proofs or sketches upon which nature practises in order to learn how to form man. In the beginning of the present century Lamarck, in Germany, following Kielmayer, reproduced the same theory. According to him all the species of animals inferior to man are but so many lower steps at which the human embryo stops in its gradual development. Man, on the contrary, is the last term reached by nature after she has travelled all through the zoological scale, to fit herself for that work. About the same time the celebrated naturalist, Stephen Geoffroy Saint Hilaire, began to disseminate in France analogous ideas under the name of stages of development (arrêt de devéloppement); and these ideas, exaggerated by some of his disciples, amounted in their minds to the same doctrine of Lamarck, just alluded to. Among them Professor Serres holds the first rank, and it is to him that Milne-Edwards alludes in the passage just cited. He expresses himself thus:
"Human organogeny is a comparative transitory anatomy, as comparative anatomy is the fixed and permanent state of the organogeny of man; and, on the contrary, if we reverse the proposition, or method of investigation, and study animal life from the lowest to the highest, instead of considering it from the highest to the lowest, we shall see that the organisms of the series reproduce incessantly those of the embryos, and fix themselves in that state which for animals becomes the term of their development. The long series of changes of form presented by the same organism in comparative anatomy is but the reproduction of the numerous series of transformations to which this organism is subjected in the embryo in the course of its development. In the embryo the passage is rapid, in virtue of the power of the life which animates it; in the animal the life of the organism is exhausted, and it stops there, because it is not permitted to follow the course traced for the human embryo. Distinct stages on the one hand, progressive advance on the other, here is the secret of development, the fundamental difference which the human mind can perceive between comparative anatomy and organogeny. The animal series thus considered in its organisms is but a long chain of embryos which succeed each other gradually and at intervals, reaching at last man, who thus finds his physical development in comparative organogeny."
Thus speaks Serres. And in another place:
"The whole animal kingdom appears only like one animal in the course of formation in the different organisms. It stops here sooner, there later, and thus at the time of each interruption determines, by the state in which it then is, the distinctive and organized characters of classes, families, genera, and species."
II.
THIS OPINION REFUTED BY PHILOSOPHICAL REASONS.
The futility of the above doctrine is manifest, in the first place, from the weakness of the foundation on which it rests. That foundation is no other than a kind of likeness which appears at first sight between the rudimental forms which, in the first steps of its development, are assumed by the human embryo, and the forms of some inferior animals. For the germ, by the very reason that it has not, as it was once believed, all the organism of the human body in microscopic proportions, but in order to acquire it must pass from potential to actual existence—by that very reason, is [{73}] subjected to continual metamorphoses, that is, to successive transformations, which give it different aspects, from that of a little disc to the perfect human figure. Now, it is clear that, in this gradual transition from the mere power to the act of perfect organization, a kind of analogy or likeness to some of the numberless forms of inferior organizations of the animal kingdom may, and must, be found in its intermediate and incomplete state.
But, evidently, between analogy and identity there is an immense difference; and the fact of there being an analogy with some of those forms, gives us no right to infer that there is one with all. Hence this theory is justly despised by the most celebrated naturalists as the whim of an extravagant fancy.
"According to Lamarck," says Frédault, in speaking of this, theory, "all the animals are but inferior grades at which the human germ stopped in its development, and man is but the result of the last efforts of a nature which has passed successively through the grades of its novitiate, and has arrived at the last term of its perfection. Presented in this view, the doctrine of epigenesis raised against itself the most simple and scientific common sense, as being manifestly erroneous. Numerous works on the development of the germ have demonstrated that appearances were taken for realities, and that imagination had created a real romance. It has been proved that if, at certain epochs of its development, the human germ has a distant resemblance either to a worm or a reptile, such resemblance is very remote, and that on this point we must believe as much as we would believe of the assertion of a man who, looking at the clouds, should say that he could discover the palaces and gardens of Armida, with horsemen and armies, and all that a heated imagination might fancy."
However, laying aside all that, the opinion which we are now examining originates, with those who uphold it, in a total absence of philosophical conceptions. That strange idea of the unity of type and of its stages, in order to establish the forms of inferior animals, would never have risen in the mind of any one who had duly considered the immutability of essences and the reason of the formation of a thing. The act of making differs from the thing made only as the means differs from the end. Both belong to the same order—one implies movement, the other rest. Their difference lies only in this: that what in the term is unfolded and complete, in its progress toward the term is found to be only sketched out, and having a tendency to formation. Hence it follows that, whatever the point of view from which we consider the embryo of each animal, it is nothing else but the total organism of the same in the course of formation; and, therefore, it differs as substantially from every other organism as the term itself toward which it proceeds. And what we affirm of the whole organism must be said of each of its parts, which are essentially related to the whole and follow the nature of the whole. The first rudiments, for instance, of the hands of man could not properly be compared to the wings of a bird. As they are hands after being made, so they are hands in the process of formation; as their structure is different, so is their being immutable.