SKULL OF A HUMAN FETUS OF 40 MM. 347 



a local adaptation. Again, at the same time (14 nfim. stage) 

 according to Levi the arch mass of the undifferentiated sclero- 

 tomes has chondrified. It would, indeed, be surprising if the 

 neural arch of the occipital vertebra were still membranous at a 

 time when the arch processes of the undifferentiated sclerotomes 

 were chondrified (those of the atlas and axis being also chondri- 

 fied), as would be the case if Levi's interpretation were correct. 

 My identification obviates this difficulty. 



Accepting this interpretation it follows that the small processes 

 or Querleisten which project laterally from the lateral processes 

 cannot be the tips of the neural arches, as Levi describes them; 

 they are really the anlagen of the transverse processes of the 

 occipital vertebra, Levi, who does not account for the dorsal 

 tips of the lateral portions of the occipital vertebra at all, is led 

 to conclude that the Querleisten represent the tips of the neural 

 arches, apparently, by the histological resemblance of their 

 tissue, in the early stages, to that composing the tips of the neural 

 arches of the underlying cervical vertebra. He remarks, how- 

 ever, that the Querleiste is very tardy in chondrifying when com- 

 pared with the neural tip of the atlas, a detail which is, if anything, 

 opposed to his identification of it as the tip of the neural arch of 

 the occipital vertebra, but is what might be expected if it be 

 homologized with a transverse process. The Querleisten are 

 shown in the Levi models to be in direct alignment with the 

 transverse processes of the cervical vertebrae, and they never 

 come together dorsally and unite, after the fashion of the dorsal 

 extremities of the neural arches. They are identical with what 

 I have called in my model the paracondyloid process, following 

 Voit, who described similar structures in the rabbit, and identi- 

 fied them as the representatives of the transverse processes, 

 also remarking that the rectus capitis lateralis muscle, which 

 each has attached to its lower surface, is to be regarded as the 

 morphological equivalent of an intertransversarius muscle. 

 Mead ('09), too, finds a similar and very strongly marked process 

 in the skull of the pig, and calls it the paroccipital process. Both 

 Levi and Voit state, correctly I befieve, that the process ulti- 

 mately becomes the jugular process of the occipital bone. . 



