88 EVOLUTION AND DOGMA. 



De Blainville, Ehrenberg, Burmeister, Von Siebold 

 and Stannius, Leuckart, Milne-Edwards, Kolliker, 

 Vogt, Van Beneden, Owen, Von Baer, Agassiz, 

 Huxley, Haeckel and Ray Lankester, not to men- 

 tion scores of others of lesser importance. 



Points of View. 



But what is more striking than the number of 

 zoological systems which our century has produced, 

 are the diverse points of view which systematists 

 have chosen in elaborating their systems. The pre- 

 Cuvierian taxonomists, as we have seen, based their 

 schemes of classification on external characteristics. 

 Cuvier insisted that taxonomy should be based on 

 internal structure, and that the structure of the en- 

 tire animal should be considered. Certain later sys- 

 tematists deemed this unnecessary, and attempted 

 to build systems of classification on the variations of 

 a single organ, or on the structure of the egg alone. 

 Again, according to Cuvier's classification, the 

 four branches of the animal kingdom are distin- 

 guished by four distinct plans of structure. Accord- 

 ing to Ehrenberg " the type of development of ani- 

 mals is one and the same from man to the monad." 

 According to Cuvier and his school, the four types 

 of structure proceed along four parallel lines. Ac- 

 cording to the evolutionary school, however, the 

 entire animal kingdom is to be conceived as a gen- 

 ealogical tree, Stanimbaum, the various branches 

 and twigs, twiglets and leaves of which, are to be 

 regarded as the classes, orders, genera and species of 

 which zoologists speak. 



