ARCHETYPE OF SKULL 149 



The other bones of the skull are not included in the 



* 



vertebrae, and this is in large part due to the fact that the 

 sense capsules are formed separately from the cranium (p. 29, 

 1838). The ear-labyrinth, it is true, fuses indissolubly with 

 the cranium at a later period, but the bones which develop 

 in its capsule are not for all that integral parts of the 

 primitive cranial vertebrae. This point, it is interesting to 

 note, had already been made by Oken in his Prograinm (1807). 

 But many of the bones developed in relation to the sense 

 organs can find their place in the generalised embryonic 

 schema or archetype of the vertebrate skull, for they are of 

 very constant occurrence during early development. 



Having arrived at a generalised embryonic type for the 

 vertebrate skull, of which the fundamental elements are the 

 three cranial vertebrae and their arches, Reichert goes on to 

 discuss the particular forms under which the skull appears 

 in adult Vertebrates. He accepts in general von Baer's law 

 that the characters of the large groups appear earlier in 

 embryogeny than the characters of the lesser classificatory 

 divisions. " When we observe new and not originally present 

 rudiments in very early embryonic stages, as, for instance, 

 that for the lacrymals, the probability is that they belong to 

 the distinctive development of one of the larger vertebrate 

 groups. From these are to be carefully distinguished such 

 rudiments as arise later during ossification, mostly as ossa 

 intercalaria, in order to give greater strength to the skull 

 in view of the greater development of the brain, etc. ; the 

 latter give their individual character to the smaller vertebrate 

 groups, and comprise such bones as the vomer, the Wonnian 

 bones, the lowermost turbinal, etc." (p. 63, 1838). 



He did not accept the Meckel-Serres law of parallelism. 

 He recognised the great similarity between the unsegmented 

 cartilaginous cranium of Elasmobranchs, and the primordial 

 cranium of the embryos of the higher Vertebrates, but he 

 did not think that the cranium of Elasmobranchs was simply 

 an undeveloped or embryonic stage of the skulls of the 

 higher forms. Rather " do the HolocepJiala, Plagiostomata, 

 and Cydostomata appear to us to be lower developmental 

 stages individually differentiated, so that the other fully 

 differentiated Vertebrates cannot easily be referred directly 



