238 
to the solution of this divergence of opinions. In studying 
the relation of the anus to the blastopore, my attention was 
drawn to the different ways in which in Anurans (Rana 
esculenta) and Urodelans (Amblystoma tigrinum) the cerebral 
plate closes. In the former there may be noted quite distinctly 
a growing up of the transverse cerebral fold, a process- 
which, at the closure of the brain vesicle, plays an equally 
important role as the growing over of the lateral cere- 
bral folds (Plate Il, fig. 3). In fig. 5 the neuropore is repre- 
sented, apparently for the first time in Anurans. At least 
Vv. KUPFFER (1906) in HERTWIG's Handbuch says concerning 
the Anurans: “Der Neuroporus ist im letzten Momente 
vor seinem Schlusse noch nicht zur Beobachtung gekommen,” 
nor is there in investigations of later date anything to be- 
found on this subject. From the situation of the recessus 
neuroporicus in median sections of later stages V. KUPFFER 
corcludes: “Es haben sich wohl die Ränder des Neuro- 
porus bei Einleitung des Schlusses einwärts gerollt und 
damit die Hirnwand zurückgelagert”. The result is a dorsal 
neuropore, corresponding in its situation to HATSCHEK's- 
“anguler” neuropore and confirming Vv. KUPFFER's views, 
since it denotes the anterior end of the dorsal suture, which 
does not continue in front of it. 
As a rule an open neuropore seems not to occur, the- 
fusion of the medullary folds being performed over their 
whole length nearly simultaneously, or, in any case, to 
have a very short-lived existence. At least in en other 
longitudinal series of similar stages I did not fin 
These processes are entirely different in the Axolotk Here 
there is hardly any question of a growing up of the transverse 
cerebral fold. The closure of the cerebral plate is exclusively 
performed by the growing up and the median fusion of 
the lateral folds. An open neuropore was not found, but an 
examination of complete eggs and sections shows conclusi- 
vely, that the anterior end of the dorsal suture, corresponding 
to the place of the neuropore, is here situated terminally, 
ust as in Petromyzon. The whole praechordal brain 
vesicle, as shown by a comparison of fig 7 and 8 of 
the plate, has in the axolotl a much more elongated shape 
and much more the character of a tube 
The animal pole not a fixed point? — Thus we see in 
two closely related groups the closure of the cerebral 
plate being performed in entirely different ways. For the 
