OF ANIMALS 



Fig. 7.1. The orders of the 

 class Amphibia. A, order 

 Caudata: the mud puppy, 

 NecluTus maculosus. B, order 

 Apoda: a caeciUan, or limbless 

 amphibian, Siphonops annulalus. 

 C, order Salientia: the pickerel 

 frog, Rana palustns. {A and C, 

 photographs courtesy New York 

 Zoological Society; 5, redrawn, 

 after Claus-Grobben, from W. 

 Stempell, 1926, ^ooiogie im 

 Grundnss.) 



Classification 



Historical. Confronted with any large array of diverse facts or forms, 

 man finds it necessary to catalog or classify them before they are under- 

 standable in relation to each other. This need to classify, to group like with 

 like, has been felt since earliest times in studies of the vast numbers of living 

 things inhabiting the earth. The first serious attempt to classify animals 

 logically and scientifically, on the basis of similarities and difTerences in funda- 

 mental characteristics, was made by Aristotle (384-322 b.c). During later 

 centuries other systems of classification were erected, and comparisons were 

 drawn between the structures of animals and those of plants. These earlv 

 systems were not widely accepted, and the classification that developed into 

 the modern scheme was not formulated until the eighteenth century. Almost 

 all the early systems suffered from the fact that relatively little was known 

 of the fundamental characteristics of living things; these svstems were based 

 largely on superficial or artificial criteria. 



In general, the classification of plants progressed more rapidly than that of 

 animals. John Ray (1628-1705) attempted to classify both animals and 

 plants in a single system, emphasizing structure as the basis of comparison. 



215 



