THE CRANIAL GANGLIA IN AMEIURUS 313 



crest cells fuse with the lateral ectoderm in two places. This was 

 confirmed for amphibia in 1886 by Misses Johnson and Sheldon, 

 who like Van Wijhe found that the dorsal fusion is connected 

 with the lateral line. 



Tn 1885 Froriep described in mammals, what he designated 

 as branchial sense organs on the facialis, glossopharyngeus and 

 vagus nerves. The epidermal thickenings which he figures and 

 designates as branchial sense organs are undoubtedly epibranchial 

 placodes since they lie immediately over the gill slits and there 

 are no lateral line nerves in the mammals. Froriep, however, 

 thinks that the resemblance of these anlagen to those of the lateral 

 line anlagen places them in that group of nerves. He further 

 finds that the evidence for the addition of cells from the placode to 

 the ganglia in these nerves is slight, since only in the earlier stages 

 are the boundaries between the two structures indistinct. 



Beard ('85, '87, '88) described primitive branchial sense organs 

 in elasmobranchs, teleosts, amphibia, reptiles and birds and also 

 stated that the epidermal thickening contributed cells to the 

 ganglia derived from the neural crest. Beard rejected the term 

 lateral line organ because the lateral lines originate in the head 

 and substituted therefor the term branchial sense organ, and he 

 seems always to have had in mind the lateral line organs of the 

 head when he speaks of branchial sense organs; at least he confuses 

 the dorso-lateral and the ventro-lateral placodes and, as von 

 Kupffer ('91) intimates, it is impossible to tell which he is discussing 

 at times. He figures and mentions, however, two points of con- 

 tact of the neural crest ganglia with the skin. 



Beard ('88, p. 882) refers to the fusion of the neural crest with 

 the epiblast at the level of the notochord, and just above the gill 

 cleft in the same paragraph, apparently not distinguishing between 

 them, although in the same paper he criticizes Onodi for not hav- 

 ing seen the second fusion of the ganglion anlage with the epi- 

 blast. It seems a safe conclusion from Beard's papers that he 

 took all fusions of the neural crest to be concerned in the forma- 

 tion of the lateral nerves. 



In discussing the origin of the neural crest portion of the ganglia 

 Beard ('88) insists that the origin of the spinal ganglia from the 



THE JOURNAL OF COMPARATIVE NEUROLOGY AND PSYCHOLOGY, VOL. 20, NO. 4. 



