150 THE TRANSFORMATIONS OF THE ANIMAL WORLD 



It may be termed the method of real evolution, 

 because it leaves as restricted a place as possible 

 for the establishment of hypothetic affiliations ; it 

 is likewise the one we have constrained ourselves 

 to follow personally in all our researches. 



But before setting forth the very interesting 

 and positive results obtained by this rigorous 

 method, it is necessary to say a few words and make 

 short work of another and more hypothetical 

 method, by means of which the history of evolution 

 becomes a sort of representative image of the changes 

 in beings, instead of corresponding to the real 

 picture of past events. This approximative method 

 has been partly employed in the works of Huxley, 

 Kowalevsky, Marie Pavlow, and in the highest 

 degree in those of Gaudry and his school. It 

 consists, when one is given a genus of existing or 

 recent animals of which we wish to study the 

 genealogy, in seeking in the series of earlier 

 geological periods for some other genera presenting 

 a certain degree of analogy with the first in the 

 structure of an organ or of a small number of 

 organs, and in composing by the help of these 

 genera an apparently natural series by the aid of 

 mere modifications of the organs thus under consider- 

 ation. In the case of the Mammals, for example, we 

 should take as criterion either the structure of the 

 molars, or of the canines, or the progressive re- 

 duction of the lateral toes, or, again, the gradual 

 development of the nasal bones, or of horns or 

 antlers, leaving on one side, or nearly so, the rest 

 of the organism. In the Ammonites, notice would 

 be taken exclusively of the greater or less com- 



