262 PRINCIPLES OF ANIMAL BIOLOGY 



1735 and 1768 and, after his death, in a thirteenth, edited by Gmelin. 

 In this work Linnaeus completed a classification which Ray had estab- 

 lished in part, giving names to important groups that Ray had left without 

 appellations, and describing animals in language which, unlike many 

 of the writings of his time, could not be misunderstood. Linnaeus also 

 had the courage to defy prejudice in such details as removing the whales 

 from the group of fishes, and placing them with the terrestrial hairy ani- 

 mals called mammals. For in the Linnsean classification structural char- 

 acters, rather than habits or external forms, were used as a basis. Six 

 categories or classes were employed, four of them vertebrate (borrowed 

 from Ra.y) and two invertebrate. These classes were divided into orders, 

 the orders into genera and the genera into species. The lesser groups 

 were usually much more inclusive than the groups now given the same 

 nominal rank. Thus, a Linnaean genus occasionally includes three or 

 four orders, as these groups are now reckoned. Moreover* the genus 

 often contained animals now placed in widely separated categories. One 

 genus was erected to include certain sea-cucumbers, a worm, a colonial 

 jellyfish, and several primitive near-vertebrates; some of these are now 

 placed near the bottom, others near the top, of the animal scale. How- 

 ever, since Linnaeus did not hold any evolutionary views, such discrepan- 

 cies did not trouble him. 



Later Temporary Systems of Classification. — Following Linnaeus, 

 many naturalists concerned themselves with systematic zoology. Some 

 of them adopted the Linnaean system in general, but altered it to suit 

 their tastes, sometimes improving it but quite as often not. Others 

 invented new classifications. Georges Cuvier (1769-1832) estabhshed 

 four major groups, called branches, which he divided into classes, nine- 

 teen in number; and some parts of his classification remained in vogue 

 in his own country for three-quarters of a century. Superior to Cuvier in 

 his conceptions was de Blainville (1777-1850) who in several instances 

 happily discovered the structural characters that were of genuine impor- 

 tance in distinguishing natural groups. He proposed a classification 

 involving three subkingdoms, distinguished by the arrangement of their 

 parts about a center or axis. These subkingdoms were the Artiomor'phes, 

 having a bilateral form like the majority of animals; the Actinomoi'phes, 

 with a radiate form like a starfish; and Heteromorphes, animals having 

 an irregular form (chiefiy Protozoa and sponges). Lamarck (1744- 

 1829) devised a classification based upon nervous sensibility, and pro- 

 posed three principal groups: the apathetic animals, those without nervous 

 systems or apparent sensation among the invertebrates; the sensitive 

 animals, also among the invertebrates; and the intelligent animals, 

 corresponding to the vertebrates. Oken (1779-1851), who was a philoso- 

 pher rather than a naturalist, advocated simultaneously at least two 

 classifications, which were equally worthless. One divided animals into 



