GENERAL PRINCIPLES OF ZOOLOGY. 



INTRODUCTION. 



Man's Relation to Other Animals. — The observant man sees him- 

 self in the midst of a manifold variety of organisms, which in their struc- 

 ture, and even more in their vital phenomena, exhibit a similarity to 

 his own being. This similarity, with many of the mammals, especially 

 the anthropoid apes, has the sharpness of a caricature. In the inverte- 

 brate animals it is softened; yet even in the lowest organisms it is still 

 to be found: although here the vital processes which have reached such 

 complexity and perfection in ourselves can only be recognized in their 

 simplest outlines. Man is part of a great whole, the Animal Kingdom, 

 one form among the many thousand forms in which animal organiza- 

 tion has found expression. 



Purpose of Zoological Study. — If we would, therefore, fully under- 

 stand the structure of man, we must, as it were, look at it upon the back- 

 ground which is formed by the other animals, and for this purpose we 

 must investigate their conditions. 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, of the different points of 

 view from which the zoologist attacks his problem. 



In the first half of the last century the conception was prevalent 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 under- 

 stood the classification of animals or systematic zoology; that is to say, 

 only one part of zoology, which can pretend to scientific value only when 

 it is brought into relation with other problems (geographical distribution, 

 variation, evolution). This conception has become more and more 

 subordinated. The ambition to describe the largest possible number of 

 new forms 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. 



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