264 ANIMAL MORPHOLOGY 



But still more than geonomy, a new science or rather an ex- 

 ceedingly rapid development of a too much neglected branch of 

 the science of morphology, should soon remedy the inevitable in- 

 sufficiency of the actual zoological principles and of our paleonto- 

 logical knowledge. 



So long as the naturalists were content to catalogue and to com- 

 pare among themselves, after the fashion of a collector of arms or 

 of objects of art, some of the many forms whose astonishing variety 

 they admire as the fruit of the inexhaustible imagination of an 

 infinitely ingenious Creator, it was to the adult states especially, 

 considered as perfect, that they directed their attention. It was of 

 little importance to them to know how the objects of their favorite 

 passion were formed. With the exception of some rare precursors 

 (Aristotle in antiquity, Malpighi, Swammerdam, Harvey, C. F. Wolff 

 in a more recent period) the majority of biologists were not interested 

 in the study of development. 



Even to-day, moreover, we find among the systematists a sort 

 of vestige of this state of mind. Among a thousand entomologists 

 how many are there who have the least interest in the collecting 

 of caterpillars or the larvae of insects? Of a hundred ornithologists 

 how many deign to admit the nests or the young of birds into their 

 collections ? 



It is not the least service that the theory of evolution has ren- 

 dered to biology that it has shown the importance and the necessity 

 of embryological studies. 



It is only fair to recognize that the ground was prepared by the 

 simultaneous development of other collateral branches of science, 

 and especially by the progress of micrography and the advent of 

 the cellular theory. 



However, we have the right to maintain that it is especially to 

 a desire to verify in a new way the ideas of Lamarck and of Darwin 

 that we must attribute the abundance and the perfection of em- 

 bryological investigations pursued after J. Miiller and von Baer, by 

 Gegenbaur, Haeckel, Leuckart, Huxley, Loeven, Van Beneden, 

 Agassiz, and others. 



By its continuity, by the dependence of its successive phases, 

 by the causal nexus which determines them and the relations among 

 themselves, the development of larva? and of embryos, or in modern 

 language, the ontogenetic series of embryological stages is marvel- 

 ously fitted to illustrate the theory of modified descent by exam- 

 ples which afford convincing evidence. 



Undoubtedly even before the publication of the works of Darwin 

 and the beautiful group of embryological monographs, of which 

 we are about to speak, Serres had foreseen, by a kind of divina- 

 tion of genius, the fruitful idea of the transitory repetition in indi- 



