FATE OF NEURAL‘CREST IN HEAD OF URODELES 7 
the precartilage cells from the nerve anlagen or from the ecto- 
derm. He denies the contribution of cells from the ectoderm 
to the mesenchyme, but does not follow the fate of neural-crest 
cells. 
Of the writers opposing Miss Platt’s hypothesis, two only, 
Corning (’99) and Buchs (’02), give sufficiently detailed descrip- 
tions and figures to enable one to estimate the value of their 
criticism. Corning certainly did not follow his stages far enough 
to determine that the mesoderm of the branchial bars is com- 
pletely surrounded by neural-crest cells. This can be seen on 
any good series of the frog, Rana pipiens. Buchs, on the other 
hand, contents himself with an effort at destructive criticism. 
His actual evidence is of a negative character, since he does not 
follow the fate of neural-crest cells that do not form ganglia. 
Of the authors who support wholly or in part Miss Platt’s 
~ contention, the earliest is Kupffer. Kupffer (95) described in 
detail and figured the cartilages in Ammocoetes as arising from 
the deeper layer of the ectoderm in the region of the branchial 
bars. He had previously (94) designated this layer as neuro- 
dermis, believing it to be concerned in the formation of the 
branchial nerves, but here designates it as branchiodermis and 
derives not only the cartilages, but goes a step farther than Miss 
Platt and derives muscles also from it. He agrees fully with 
Miss Platt’s interpretation after examining her preparations. 
He further derives mesenchyme in the dorsal anterior head regions 
from the neural crest. 
Lundborg (99) derived the pterygopalatine cartilages in 
Salmo salar and the trabeculae in Rana temporaria from the 
ectoderm of the roof of the mouth. He also derived the ethmoid 
cartilages in Salmo in the same manner. The anterior end of 
these cartilages in Salmo are in process of formation in sixty- 
eight-day-old embryos. 
Koltzoff (02), in Petromyzon, derives mesenchyme in the 
head from both the neural crest and lateral ectoderm, but is 
unable to follow its fate beyond the point of the mingling of 
- ectodermal cells with those derived from endoderm. 
