FATE OF NEURAL CREST IN HEAD OF URODELES 3 
persist up to so late a stage in development in certain regions of 
the head that it can be determined accurately that head struc- 
tures, usually considered as of mesodermal origin, are derived 
from the ectoderm of the neural crest. 
HISTORICAL SKETCH 
The idea that ectodermal cells, derived from either neural 
crest or from the lateral ectoderm, can be traced into permanent 
head: structures, other than ganglia, was first stated definitely 
by Miss Platt in 1893. It was claimed in a preliminary paper 
published by her at that time that branchial cartilages arose 
from ectodermal cells. Before the appearance of her paper, 
however, several papers appeared bearing more or less directly 
on the fate of the non-nervous portion of the neural crest. Mar- 
shall (78), working on the chick, and van Wijhe (’82), on the 
selachians, both called attention to the fact that the neural crest 
is present in the head anterior to the trigeminus ganglion, but 
could not determine the fate of that portion of the crest which 
does not enter into the formation of that ganglion. 
Kastschenko (’88) went a step farther and stated that, in the 
head of the selachian embryo, other layers than the endoderm, 
particularly the ectoblast, take part in the formation of mesen- 
chyme, and that in the formation of the neural crest some of the 
cells detach themselves from the neural-crest mass, become 
loosely arranged, and form mesenchyme, while other cells from 
the same source are concerned in the formation of ganglia. The 
further fate of the mesenchymal cells is not discussed, neither is 
their relation to mesenchyme derived from endoderm treated. 
Goronowitsch (’92) published a preliminary paper in which 
he determined for birds not only that the neural-crest cells give 
rise to mesenchyme in the head region, but that they fuse with 
the axial mesoderm derived from the endoderm to form a homo- 
geneous mesenchyme in which neural-crest cells can no longer be 
distinguished. He also noted a _ proliferation of mesoderm 
(mesenchyme?) cells from the ectoderm in the dorsal portion of 
the gill. 
