268 ANIMAL MORPHOLOGY 



is material for numerous problems of very vital interest for those 

 who do not wish to content themselves with the easy but childish 

 solution of final causes. 



"Voir venir les choses," Savigny has said, "est la meilleure fagon 

 de les observer. " Morphology, in brilliantly illuminating comparative 

 anatomy, makes possible the rectification of numerous errors of tax- 

 onomy and the better appreciation of the value of different taxonomic 

 groupings. But at the same time that they aided in the advancement 

 of normal morphology, embryological studies, extended to abnormal 

 forms of development, demonstrated the great influence of the science 

 of monstrosities or teratology. Soon, thanks to the patient investiga- 

 tions of Dareste and to the abilities of Chabry and W. Roux in the 

 artificial production of animals, teratology became an experimental 

 science, and it was from that time easy to understand how in inter- 

 vening in a more or less constant manner at different periods of onto- 

 geny the cosmical or biological factors have gradually been able to 

 modify the larval forms and indirectly the adult forms of living beings. 



As a result of the science of the habits and relations of living beings 

 either among themselves or with the cosmical environment, ethology 

 or bionomy, somewhat neglected since the time when Reaumur, De 

 Geer, etc., cultivated it with so much success, gains a new interest and 

 offers to every biologist a collection of experiments prepared by nature 

 and of which it is necessary only to interpret the results. 



Is it not remarkable indeed to see the bionomy of the adult modify 

 the development of the embryo so profoundly as sometimes to hide, 

 in the course of evolution, the affinity which exists among related 

 forms? 



Does not the vegetable or animal diet of a mammal, for example, 

 follow as a consequence primarily of the state of perfection at birth 

 and also of the abbreviation of the embryological processes, since the 

 young are not sufficiently protected by their parents, whose rapid 

 movements in search of nourishment or for the avoidance of an enemy 

 they must follow? 



The animals which are fixed in the adult state, and especially para- 

 sites, which early establish themselves upon the host and never leave 

 it, necessarily have an explicit development, and the motile larva? are 

 provided with organs of sense which permit them to choose with care 

 the resting-place where the greater part of their existence will pass. 

 On the contrary, in pelagic beings, which early in life are exposed to 

 a thousand dangers, there would be every reason why the progeny 

 should be protected by direct, rapid and coenogenetic development or 

 be trusted to a strange nurse, as is the case with the copepods of the 

 group MonstrillidfE. Even evolutionary phenomena as complicated 

 as those in the Coleopteran, Meloides, under the name of hyper- 

 metamorphosis, become easy of explanation if we view them in their 



