FATE OF NEURAL CREST IN HEAD OF URODELES 9 
the gill bar is performed by cells derived from the neural crest. 
Brauer objects to Miss Platt’s terms mesectoderm and mesento- 
derm which had been accepted by Dohrn and Koltzoff. He 
reserves his description of the ultimate fate of the ectodermal 
mesenchyme of the gill bar for a later paper and consequently 
does not describe the origin of definite cartilage. 
An impartial examination of the papers cited above furnishes 
strong evidence for the formation of the mesenchyme in the 
anterior head region in the embryo from both endodermal 
(mesentoderm) and ectodermal (mesectoderm) sources. In all 
cases the fate of these individual cells is lost and it is not possible 
to determine the extent to which either or both of them is con- 
cerned in the formation of adult mesenchyme in this region. 
However, evidence for the disappearance of mesectoderm cells 
in the anterior head region is conspicuously absent. The same 
statement holds in the main for the dorsal mesenchyme in the 
posterior portion of the head. 
The fate of the ectodermal derivatives in the branchial regions 
is much more definitely stated. Platt (93), Kupffer (95), 
Brauer (’04), and Dohrn (’02), all derive either the cartilages 
and mesenchyme or both cartilages and muscles in addition to 
mesenchyme from the ectoderm. Platt (’93), Kupffer (95), and 
Koltzoff (’02) derive the ectodermal cells in the branchial region 
largely or even altogether from the lateral ectoderm, while 
Brauer (’04), Corning (’99), and Buchs (’12) can find no evidence 
for the proliferation of cells from the ectoderm, and Brauer (’04) 
and Dohrn (’02) derive the structures in the branchial bar 
entirely so far as they are ectodermic from the neural crest. _ 
MATERIAL 
The material on which the work was‘done consists of three 
series of urodele embryos collected in the same pond, but repre- 
senting at least two different species. The youngest series 
(series I) consists of thirty-five stages taken from two egg clusters 
at intervals of five to five and one-half hours, reared at room 
temperature, and covers an interval of eight days. The first 
