12 EARLY PROGRESS 



different foundations may teach us that every 

 structural combination includes certain inherent 

 necessities which will bring animals together on 

 whatever set of features we try to classify them ; 

 so that the division of Aristotle, founded on the 

 circulating fluids, or that of Lamarck, founded on 

 the absence or presence of a backbone, or that of 

 Ehrenberg, founded on the differences of the ner- 

 vous system, covers the same ground. Lamarck 

 attempted also to make the faculties of animals a 

 basis for division among them. But our knowl- 

 edge of the psychology of animals is still too 

 imperfect to justify any such use of it. His 

 divisions into Apathetic, Sensitive, and Intelligent 

 animals are entirely theoretical. He places, for 

 instance, Fishes and Reptiles among the Intelli- 

 gent animals, as distinguished from Crustacea 

 and Insects, which he refers to the second division. 

 But one would be puzzled to say how the former 

 manifest more intelligence than the latter, or why 

 the latter should be placed among the Sensitive 

 animals. Again, some of the animals that he 

 calls Apathetic have been proved by later investi- 

 gators to show an affection and care for their 

 young, seemingly quite inconsistent with the epi- 

 thet he has applied to them. In fact, we know 

 so little of the faculties of animals that any classi- 

 fication based upon our present information about 

 them must be very imperfect. 



