CLASSIFICATION 39 



such a character that it does not destroy the harmony of the 

 whole." l We seize here the relation of the principle of the 

 adaptedness of parts to the problem of the variety of form. 

 The former is in a sense a regulative and conservative 

 principle which lays down limits beyond which variation may 

 not stray. In itself it is not a fountain of change; there 

 must be another cause of change. This thought is of great 

 importance for theories of descent. 



Cuvier has no theory to account for the variety of form : 

 he contents himself with a classification. There are two 

 main ways of classifying forms ; you may classify according 

 to single organs or according to the totality of organs. By 

 the first method you can have as many classifications as you 

 have organs, and the classifications will not necessarily 

 coincide. Thus you can divide animals according to their 

 organs of digestion into two classes, those in which the 

 alimentary canal is a sac with one opening (zoophytes) 

 and those in which the canal has two openings,' 2 a curious 

 forestalment, in the rough, of the modern division of 

 Metazoa into Coelentera and Ccelomata. 



It is only by taking single organs that you can arrange 

 animals into long series, and you will have as many series 

 as you take organs. Only in this way can .you form any 

 EcJielle dcs ctres or graded series ; and you can get even 

 this kind of gradation only within each of the big groups 

 formed on a common plan of structure; you can never grade, 

 for example, from Invertebrates to Vertebrates through 

 intermediate forms 3 (which is perfectly true, in spite of 

 Amphioxus and Balanoglossus !). 



In the Rcgnc Animal Cuvier restricts the application of 

 the idea of the Ecliellc within even narrower limits, refusing 

 to admit its validity within the bounds of the vertebrate 

 phylum, or even within the vertebrate classes. This seems, 

 however, to refer to a seriation of whole organisms and not of 

 organs, so that the possibility of a seriation of organs within a 

 class is not denied. Cuvier was, above all, a positive spirit, and 

 he looked askance at all speculation which went beyond the 

 facts. " The pretended scale of beings," he wrote, " is only 



1 Lemons, i., p. 58. '-' Loc. cif, i., Article iii. 



3 Loc. cit., i., p. 60. 



D 



