252 ESSAY ON CLASSIFICATION. 



has never assisted any anxious and conscientious naturalist 

 in investigating the degree of relationship between closely 

 allied animals or plants living in distant regions or in dis- 

 connected geographical areas. It will never contribute 

 to the solution of any of those difficult cases of seeming 

 difference of identity between extinct animals and plants 

 found in different geological formations. In all critical 

 cases, requiring the most minute accuracy and precision, 

 it is discarded as unsafe, and of necessity questionable. 

 Accurate science must do without it; and the sooner it 

 is altogether discarded, the better. But, like many relics 

 of past time, it is dragged in as a sort of theoretical bug- 

 bear, and exhibited only now and then to make a false 

 show in discussions upon the question of the unity of 

 origin of mankind. 



There is another fallacy, connected with the prevailing 

 ideas about species, to which I would also allude, the 

 fancy that species do not exist in the same way in nature 

 as genera, families, orders, classes, and types. It is 

 actually maintained by some, that species are founded in 

 nature in a manner different from these groups ; l that 

 then- existence is, as it were, more real, whilst that of the 

 other groups is considered as ideal, even when it is ad- 

 mitted that these groups have themselves a natural 

 foundation. 



Let us consider this point more closely, as it involves 

 the whole question of individuality. I wish, however, 

 not to be understood as undervaluing the importance of 

 sexual relations as indicative of the close ties which unite, 

 or may unite, the individuals of the same species. I 

 know as well as any one to what extent they manifest 

 themselves in nature, but I mean to insist upon the un- 



1 BuiiMEisTEii (II.)) Zoon. Briefe, q. a v vol. 1, p. 11. 



