6 F, L. LANDACRE 
its cells from that source, but in Rana it does not break down 
into mesenchyme, according to this author. The mesenchyme 
of the head is derived from the endoderm, and is consequently 
mesentoderm in Miss Platt’s sense of this word or mesoderm 
in the older sense. 
Minot (’01), in an address before the New York Pathological 
Society, makes a vigorous defense of the doctrine of the integrity 
of the germ layers, in which he agrees with Rabl (’94), whose 
opinion was expressed under somewhat similar circumstances. 
He calls attention to Miss Platt’s work specifically and says, 
“‘an examination of a number of series and stages has not enabled 
me to find the slightest evidence in favor of Miss Platt’s con- 
clusions.”” He says further that ‘‘we may, therefore, I think 
safely regard this attempt to overthrow the morphological value 
of the germ layers as unsuccessful. I know of no other attempt 
of sufficient importance to be even mentioned.” He states in an 
earlier paragraph that ‘‘the efforts to upset the validity of this 
fundamental doctrine have failed to find support or recognition 
from any leading embryologist.”” These statements of Doctor 
Minot’s were made previous to the appearance of the work by 
(Dohrn (’02) and Brauer (’04), but after the appearance of that 
of Kupffer (95) which he must have overlooked. Both Minot 
and Rabl seem, in the opinion of the writer, to have given too 
much weight to the doctrine of the integrity of the germ layers 
in their estimate of a question, which is purely one of accuracy 
of observation and description. 
Buchs (’02), after studying Necturus, disagrees with Miss 
Platt’s conclusions, taking exception particularly to her state- 
ments concerning the derivation of mesenchyme from the lateral 
ectoderm and to her distinction between mesectoderm and 
mesentoderm on the basis of the amount and size of the yolk 
granules. Buchs’ opposition to Miss Platt’s interpretation of 
the mesenchyme is based frequently on minor details and possible 
ambiguities in statements, although he has worked over the 
same type. He derives cartilage from mesenchyme which arises 
from endoderm by a folding process of the endoderm and not 
from ectoderm. He can find no evidence for the wandering of 
