CRITICISM OF VERTEBRAL THEORY 157 



lying in front of this cannot themselves be vertebrae, though 

 they may be considered as prolongations of the occipital 

 or nuchal vertebra. " We must regard the nuchal plate as 

 a true vertebra, modified, it is true, in its formation and 

 development by its particular functions. Now, since the 

 notochord ends with the nuchal plate we can no longer 

 regard as vertebrae the parts of the skull that lie beyond, 

 such as the lateral processes of the cranium and the facial 

 plate, for they have no relation with the notochord " (p. 123). 



To support this view he adduced the fact that the vertebral 

 divisions (primitive vertebras) visible in the trunk do not 

 extend into .the head. He used precisely the same arguments 

 in his paper on Alytes to destroy the vertebral theory of the 

 skull. We quote the following passage translated by Huxley 

 (1864, p. 295) from this paper. " It has therefore become my 

 distinct persuasion that the occipital vertebra is indeed a true 

 vertebra, but that everything which lies before it is not 

 fashioned upon the vertebrate type at all, and that efforts to 

 interpret it in such a way are vain ; that, therefore, if we 

 except that vertebra (occipital) which ends the spinal column 

 anteriorly, there are no cranial vertebrae at all." 



L. Agassiz, himself a pupil of Dollinger, in the general 

 part (1844) of his Recherches sur les Poissons fossilcs 

 (Neuchatel, 1833-43), repeats in the main his pupil Vogt's 

 criticism of the vertebral theory (vol. i., pp. 125-9). 



These arguments of Vogt and Agassiz were not considered 

 by Muller to dispose of the theory, 1 which maintained a firm 

 hold even upon embryologists. It was still upheld by 

 Reichert, and Kolliker in 1849 showed himself convinced of 

 its general validity. 



A useful step in the analysis of the concept " vertebra " 

 was taken by Remak, 2 who showed what a complex affair the 

 formation of vertebrae really is, involving as it does a complete 

 resegmentation (Neuglie'derung] of the vertebral column, 

 whereby the original vertebral bodies were replaced by the 

 secondary definitive bodies (p. 143). Remak showed, as he 

 thought, that the protovertebral segmentation of the dorsal 



1 Miiller's Archiv for 1843, p. ccxlviii. 



! Unfersuchungcn iibcr die Entivickelung dcr Wirbelthierc, Beilin, 

 1850-55. 



