HOMOLOGY 109 



type; when, for example, the correspondence of the basilar 

 process of the human occipital bone with the distinct bone 

 called ' basi - occipital ' in a fish or crocodile is shown, the 

 special honiology of that process is determined. A higher 

 relation of homology is that in which a part or series of parts 

 stands to the fundamental or general type, and its enunciation 

 involves and implies a knowledge of the type on which a 

 natural group of animals, the Vertebrate, for example, is 

 constructed. Thus when the basilar process of the human 

 occipital bone is determined to be the ' centrum ' or ' body ' 

 of the last cranial vertebra, its general homology is enunciated. 



" If it be admitted that the general type of the vertebrate 

 endoskeleton is rightly represented by the idea of a series of 

 essentially similar segments succeeding each other longi- 

 tudinally from one end of the body to the other, such 

 segments being for the most part composed of pieces similar 

 in number and arrangement, and though sometimes extremely 

 modified for special functions, yet never so as to wholly 

 mask their typical character then any given part of one 

 segment may be repeated in the rest of the series, just as one 

 bone may be reproduced in the skeletons of different species, 

 and this kind of repetition or representative relation in the 

 segments of the same skeleton I call ' serial homology ' 

 (p. 7). As an example of serial homology we might take the 

 centra of the vertebras the vomer, the presphenoid, the 

 basisphenoid, the basioccipital and the series of centra in the 

 spinal column. Such serially repeated parts are called 

 homotypes (p. 8). 



Not all the bones of the vertebrate skeleton are included 

 in the archetype as constituents of the vertebrae. Thus the 

 branchial and pharyngeal arches are accounted part of the 

 splanchnoskeleton, as belonging to the same category as the 

 heart bone of some ruminants, and the ossicles of the stomach 

 in the lobster (p. 70). The ossicles of the ear in mammals 

 are "peculiar mammalian productions in relation to the 

 exalted functions of a special organ of 'sense " (p. 140, f.n.). 

 This recognition of a possible development of new organs to 

 meet new functions shows unmistakably the influence of 

 Cuvier. Owen was indeed well aware of the importance of 

 the functional aspect of living things, and he often adopted 



