240 .THE NATURE AND ORIGIN OF LIFE 



men still feel the need of cataloguing, in strictly limited 

 pigeon-holes, all these highly variable bodies called living 

 beings. Evidently, such classification is indispensable in 

 the narration of facts ; but it is good enough for the pur- 

 pose when it is clear and easy to handle. There is no neces- 

 sity of asking whether our catalogue pigeon-holes are 

 separated off by some principle of higher philosophy or 

 some absolute definition of species already existing before 

 men undertook to classify. 



Yet even nowadays men ask what species is, instead of 

 using their liberty to define the groups in which, for their 

 own personal convenience, they shut up all living beings. 



Cuvier's definition of species is still currently taught 

 " The collection of all the organized beings descending from 

 each other or from common parents and of those resem- 

 bling them as much as they resemble each other." 



This is a definition after the fact and not a priori, such 

 as ought to be made when we have a catalogue classifica- 

 tion on hand. In reality, it is not a definition at all, but 

 a biological theorem and not strictly true at that. If we 

 dissect Cuvier's proposition we find first, our intuitive 

 idea of beings of the same species ; then a theorem that 

 children are of the same species as their parents. 



It goes without saying that Cuvier's definition, or rather 

 the theorem hidden in it, is the denial of Transformism. 

 If we accept in its strict sense the proposition "children 

 are of the same species as their parents " we shall have 

 to reason, step by step, to the necessary conclusion that 

 the animals of the present day are of the same species as their 

 remotest ancestors. Unluckily, people do not generally 

 look so close in natural sciences and, in all courses of zoology, 

 pupils are still taught together Transformism and Cuvier's 

 definition ! 



