AMPHIBIAN NERVOUS SYSTEM 



395 



characteristics in the cells of visceral arch cartilage, and to have 

 traced them back to the neural crest cells^ (figs. 190, 191). 



Experiments in which the neural crest cells were stained intra 

 vitam have not yet demonstrated the presence of the stain actually 



l.CBR. 



Fig. 191 

 Chondrocranium of a larva of Rana palustris from which the neural crest was 

 removed on the right-hand side; note reduction of trabecula and visceral arches. 

 Letters as in fig. 190. Also: IR. infra-rostral; PO. pterygo-quadrate; SR. 

 supra-rostral. (From Stone, Arch. Entwmech. cxviii, 1929.) 



in the cartilage cells, although the colour can be seen in the correct 

 position in the living state. ^ Presumably, by the time the cartilage 

 is differentiated, the stain has beerf dissipated. However, definite 

 proof of this potentiality of neural crest cells has recently been 



1 For the morphological bearing of these facts, see de Beer, 1930. 



2 Stone, 1932. 



