262 ANIMAL MORPHOLOGY 



istic form to the propositions for all of which the evidence is perhaps 

 not sufficient. A more complete demonstration would have required 

 the lengthiness that I have insisted on avoiding. My conviction, 

 too decisively and perhaps too strongly expressed, is based in every 

 case upon mature reflection and upon the experience of long years 

 of study. 



Certainly the change of orientation introduced into the natural 

 sciences by the transformation theory does not detract from the 

 positive value of the results previously acquired by the purely 

 descriptive method, and we cannot overlook the materials slowly 

 accumulated by our predecessors. We can continue to proclaim 

 accord in this matter with Cuvier: "La determination precise des 

 especes et de leurs caracteres distinctifs fait la premiere base sur 

 laquelle toutes les recherches de 1'histoire naturelle doivent etre 

 fondles; les observations les plus curieuses, les vues les plus nou- 

 velles perdent presque tout leur me"rite quand elles sont de"pour- 

 vues de cet appui; et malgre* I'aridit6 de ce genre de travail, c'est 

 par la que doivent commencer tous ceux qui se proposent d'arriver 

 a des result ats solides." 



A great number of naturalists devoted to the systematic study 

 of morphology received the idea of the variability of species with 

 mistrust, thinking that this idea undermines the principles upon 

 which their science of predilection rests. Events have not been slow 

 in proving that these fears were chimerical. In order to demon- 

 strate scientifically the reality of variations often very slight at 

 first, it was necessary to be more precise than formerly, and some- 

 times even to give minute descriptions of the forms under discus- 

 sion. The preservation of types in collections and museums, their 

 graphic representation and their careful comparison with related 

 species became more and more prominent, and certainly the ad- 

 vances of systematic natural history have been strongly stimulated 

 by the disputes of the partisans and the adversaries of the theory of 

 descent. 



The study of new forms, the search for intermediate types, abnor- 

 malities, mutations, local varieties, no longer have as their sole 

 purpose the satisfaction of a vague feeling of curiosity. The know- 

 ledge of slight modifications of structure, of slight steps in normal 

 morphology, have become precious elements for the construction 

 of phylogenetic trees. 



Natural classification, instead of being a subjective entity, variable 

 with the conceptions peculiar to each systematist. is now presented 

 to the mind as an objective reality: the genealogical history of 

 living beings of which we can already conceive a general plan, very 

 imperfect undoubtedly, but for the establishment of which all later 

 discoveries should cooperate. 



