525 



[orraly manifested. Without any change of shape, it would obv\ 

 onsly have been quite possible for every actual vertebra to hme 

 contained all the parts of the ideal one — rudimentally where they 

 were not wanted. Even oae of the terminal bones of a mammal's 

 tail might have been formed out of the nine autogenous pieces, 

 united by suture but admitting of identification. As, however, 

 there is no such uniform typical repetition of parts, it seems to us 

 that to account for the typical repetition which does occur, by sup- 

 posing the Creator to have fixed on a pattern-vertebra, is to ascribe 

 to liim the inconsistency of forming a plan and then abandoning it. 

 If, on the other hand, Professor Owen means that the " ideal 

 typical vertebra" is a crystalline form in antagonism with " the 

 idea or organizing principle ;" then we might fairly expect to find 

 it most clearly displaying its crystalline character, and its full com- 

 plement of parts, in those places' where the organizing principle 

 may be presumed to have " subdued " it to the smallest extent. 

 Yet in the Vertebrata generally, and even in Professor Owen's 

 Archetypus, the vertebrae of the tail, which must be considered as, 

 if anything, less under the influence of the organizing principle 

 than those of the trunk, do not manifest the ideal form more com- 

 pletely. On the contrary, as we approach the end of the tail, the 

 successive segments not only lose their remaining typical elements, 

 but become as uncrystalline-looking as can be conceived. 



Supposing, however, that the assumption of suppressed or unde- 

 veloped elements be granted — supposing it to be consistent with 

 the hypothesis of an " ideal typical vertebra," that the constituent 

 parts may severally be absent in greater or less number, sometimes 

 leaving only a single bone to represent them all ; may it not be that 

 such parts as are present, show their respective typical natures by 

 some constant character : say their mode of ossification ? 



To this question some parts of the Archetype and Hcmiologies seem 

 to reply, " Yes ;" while others clearly answer, " No." Criticising 

 the opinions of Geoffroy St. Hilaire and Cuvier, who agreed in 

 thinking that ossification from a separate centre was the test of a 

 separate bone, and that thus there were as many elementary bones 

 in the skeleton as there were centres of ossification. Professor Owen 

 points out that, according to this test, the human femur, which is 

 ossified from four centres, must be regarded as four bones ; while 

 the femur in birds and reptiles, which is ossified from a single 

 centre, must be regarded as a single bone. Yet, on the other hand, 

 he attaches weight to the fact that the skull of the human foetus 

 presents " the same ossifio centres " as do those of the embryo kan- 

 garoo and the young bird {Nature of Limbs, p. 40.) And at p. 

 104 of the Homologies, after giving a number of instances, he says — 



' Theae and the like correspondences between the points of ossification of 



