266 Mr. H. G. Seeley on the Origin 



the different types of skeletons. This has in old times made 

 the comparative anatomy of these living animals more a study 

 of the soft vital tissues than of the hard osseous structures, 

 with which alone the fossil tyjDes of life can be compared. It 

 has also had a tendency to make the skeleton seem important 

 chiefly as an index to the nervous or respiratory or other 

 organization of the animal to which it pertains. The skeleton, 

 however, has a distinct morphological importance of its own 

 in classification, probably as significant of near affinity as any 

 part of the organism. And in the endeavour to determine the 

 relations of affinity to each other of the fossil groups, and 

 their zoological position, it will be necessary to adhere to this 

 simple morphological test, as well as to apply it to the living 

 ordinal groups, which will hereafter be examined. 



The skeleton nevertheless often, in some of its elements, 

 manifests convincing evidence of the condition of some of the 

 soft parts, being subservient to them ; and this gives an 

 empirical evidence of affinity which the traditional practice of 

 anatomists would warrant us in valuing highly. Still that 

 estimate of the soft parts of an animal which makes the salient 

 features of all animal classifications will admit of question, and 

 may even seem artificial, when animals are considered in 

 all their affinities. At present, classifications, so far as they 

 are consistent and logical, only express what may be named 

 the lateral affinities of groups of animals — that is, their resem- 

 blance to others which are upon the same horizon of organi- 

 zation. But some animal orders also have affinities with 

 other animal orders which are both above and below them in 

 complexity of structures. And if any form of creation by 

 physical and chemical law is admitted into the domain of 

 science, then the affinities which are indicative of evolution 

 must obviously afford a more philosophical ground for classi- 

 fication than those affinities which merely show the parallelism, 

 in their successive stages, of groups of organisms which are 

 parted from each other by inevitable gaps, chasms comparable 

 to those which (as a small illustration) divide from each other 

 the phalanges of the successive digits. 



So that we may regard the final problem of comparative 

 osteology as the production, under laws, of a calculus of affi- 

 nities of animals, in which their relations to each other will 

 be manifest in a classification which transcribes nature her- 

 self. 



In the following pages a sketch is made of the way in 

 which such a philosophy may be led up to by a consideration 

 of the bones and the fundamental conditions which determine 

 their relations to each other. 



