22 THE MODERN STUDY OF ZOOLOGY 



animals is the goal towards the attainment of which 

 the efforts of zoologists are directed. 



Having traced the way in which this idea arose, 

 how increase of knowledge and perfection of 

 methods caused classification by definition to re- 

 place the crude ideas embodied in the classifications 

 adopted by Solomon and Pliny, and then in its turn 

 to give way to classification by type, and having 

 seen how finally the doctrine of natural selection 

 rendered possible the conception of a genetic 

 classification, it may not be out of place to devote 

 a few words to considering the methods by which 

 it is proposed to attain this end. These are as 

 follows : 



1. The accumulation of anatomical facts con- 

 cerning as large a number of animals as possible ; 

 this requires no further explanation. 



2. The systematic study of the geographical 

 distribution of the different animals and groups of 

 animals, both recent and extinct. This, which is 

 a comparatively new branch of zoology, has already 

 yielded results of immense importance, and pro- 

 mises to yield others of even greater value in the 

 future. 



3. Palaeontology, or the study of the anatomy 

 of extinct animals and their relations to existing 

 forms. We have seen above that it is to palaeon- 

 tology that we owe the first successful attempt to 

 reconstruct the pedigree of some one given form ; 

 and inasmuch as the connecting links between the 

 several groups of animals are almost necessarily 

 extinct, it is clear that the evidence yielded by 



