FATE OF NEURAL CREST IN HEAD OF URODELES 23 
neural crest is concerned in the formation of ectodermal mesen- 
chyme and cartilages. 
This problem must be settled finally, of course, by observa- 
tion; but since my results agree with those of Dohrn and Brauer, 
and since I have examined carefully types in which some authors 
derive mesenchyme from lateral surface ectoderm, it is interesting 
to examine conditions in the lateral ectoderm, which might have 
led to a misinterpretation of the facts by earlier authors. 
The lateral ectoderm is concerned in the formation of a number 
of structures which do not form mesenchyme and their number 
and significance are impressive. These structures, taken approxi- 
mately in the order of their sequence in development, are as 
follows: 
a. In the early stages of the formation of the neural plate a 
few scattered cells lie between the lateral border of the neural 
plate and the thin surface ectoderm, but they are few in number 
and show every appearance of detached neural-crest cells. In 
the later migration ventrally of the neural crest they are either 
lost or incorporated with the neural crest. They certainly fur- 
nish no evidence for a general contribution of cells to the mesen- 
chyme from the lateral ectoderm. 
b. The profundus ganglion arises from the lateral ectoderm 
anterior to the gasserian ganglion and is quite extensive both 
in its longitudinal and its vertical diameters and shows at times 
the appearance of an extensive delamination. A careful study 
of its development shows, however, that the delamination of 
the ectoderm at this point is concerned solely with the formation 
of the profundus ganglion and not with mesenchyme. 
c. The lateral ectoderm next gives rise to the lateral-line 
ganglion of nerves VIJ, IX, and X in certain types, and espe- 
cially in those types in which the homologue of the neural crest 
is not included in the neural canal (type III, p. 11). These 
forms present the appearance of contributing cells to the mesen- 
chyme. Their true fate, however, can be determined to be the 
formation of lateral-line ganglia, if one has a complete series 
- taken at close intervals. 
