2 GENERAL PRINCIPLES OF ZOOLOGY. 



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

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

 versal, 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 

 classification of animals, that is to say, only one .part of zoology, 

 indeed a part of minor importance, which can pretend to scientific 

 value only when it is brought into relation with other problems 

 (geographical distribution, evolution). This conception has 

 during the past five decades become more and more subordinated. 

 The ambition to describe the largest possible number of new forms 

 and to shine by means of an extensive knowledge of species belongs 

 to the past. In fact there is a tendency to undue neglect of 

 classification. 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 has first to describe all which can be seen exter- 

 nally, 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 

 morphologist must make these accessible by the aid of dissection, 

 of Anatomy, and likewise describe their forms and methods of 

 combination. In his investigation he only stops when he has 

 arrived at the morphological elements of the animal body, the 

 cells. Everywhere the morphologist has to do with conditions of 

 form: the only difference lies in the instruments by means of 

 which he obtains his insight, according to whether he gathers his 

 knowledge through immediate observation, or after a previous 

 dissection with scalpel and scissors, or by use of the micro- 

 scope. Therefore we cannot contrast Morphology and Anatomy, 

 and ascribe to the former the description of only the external, and 

 to the latter of only the internal parts. The distinction is not 

 logically correct, since the kind of knowledge and the mental 

 processes are the same in both cases. The distinction, too, is 

 unnatural, since in many instances organs which in some cases lie 

 in the interior of the body, and must be dissected out, belong in 

 other cases to the surface of the body, and are accessible for direct 

 description. Further, on account of their transparency the in- 

 ternal parts of many animals can be studied without dissection. 



Comparative Anatomy. For morphology, as for every science, 

 the proposition is true that the mere accumulation of facts is not 



