CRANIAL GANGLIA OF AMBLYSTOMA 



477 



ther ventrally and then cease. They may be remnants of crest 

 cells which adhered to the outer border of the mesoderm at the 

 time of operation. However, their number is insignificant com- 

 pared to the amount of similar cells on the normal side. The 

 crest cells around the mesoderm of the hyoid arch are also con- 

 siderably less in amount than on the normal side. 



Case 2. The operation was done at the same stage as in the 

 previous case and the specimen was killed after six days. A 

 frontal section (fig. 69), although somewhat oblique, shows in the 



68 



69 



Fig. 68 Frontal section through the mesoderm of hyoid, first and second 

 branchial arches, showing, three days after removal of crest cells, no crest cells 

 on right side. X 37. 



l^fFig. 69 Frontal section of specimen killed six days after removal of crest 

 cells in hyoid and branchial regions, showing a distinct lack of crest cells on right 

 side around the mesoderm of hyoid and first and second branchial arches. X 37. 



Fig. 70 Frontal section of specimen killed nine days after removal of crest 

 cells over the hyoid and branchial regions, showing only three procartilage cells 

 in the third branchial arch. X 37. 



Fig. 71 Frontal section at a lower level in the same specimen as in figure 70, 

 showing only a few procartilage cells in the hyoid and first branchial regions. 

 X 37. 



