2 GENERAL PRINCIPLES OF ZOOLOGY. 



But meanwhile the subject of Zoology has widened ; for, 

 apart from its relations to man, Zoology has to explain 

 the organization of animals and their relations to one 

 another. This is a rich field for scientific activity; its 

 enormous range is a consequence, on the one hand, of the 

 well-nigh exhaustless variety of animal organization, and, 

 on the other hand, of the different points of view from 

 which the zoologist enters upon the solution of his 

 problem. 



In the first half of this century the conception, which is 

 still held by the public at large, was prevalent, if not quite 

 universal, in scientific circles, that the aim of Zoology is 

 to furnish every animal with a name, to characterize it 

 according to some easily recognizable features, and to 

 classify it in a way to facilitate quick identification. By 

 Natural History was understood the systemization of ani- 

 mals, that is to say, only one part of Zoology, indeed a 

 part of minor scientific importance. This conception has 

 during the past four decades become more and more sub- 

 ordinated. The ambition to describe the largest possible 

 number of new forms and to shine by means of an exten- 

 sive knowledge of species belongs to the past. In fact 

 there is a tendency to undue neglect of systemization. 

 Morphology and Physiology to-day dominate the sphere 

 of the zoologist's work. 



Morphology, or the study of form, begins with the 

 appearances of animals, and particularly has to describe all 

 which can be seen externally, as size, color, proportion of 

 parts. But since the external appearance of an animal 

 cannot be understood without knowledge of the internal 

 organs which condition the external form, the morphol- 

 ogist must make these accessible by the aid of dissection, 

 of Anatomy, and likewise describe them according to their 

 form and method of combination. In his investigation he 

 stops only when he has arrived at the morphological ele- 

 ments of the animal body, the cells. Everywhere the 

 morphologist has to do with conditions of form : the only 

 dihei'ence lies in the instruments by means of which he 



