1263 
cerebral fold) to the slit-like blastopore measured ventrally being 
much less than 180°. In accordance with this the dorsal blastopore 
lip, as fig. 5 (plate) compared to fig. 1 (plate) shows, and the 
archenteron are developed very strongly, the ventral blastopore lip 
and the so-called anal diverticulum very little. Yet both the latter 
are still easily recognisable and on the outside of the ventral lip, 
a little distance behind the blastopore, a small depression of the 
ectoderm (a) may even be noted, where the future anus might be 
expected, if things happened in the same- way as in Anurans. 
Immediately behind that shallow depression we find here again the 
same thickening of the ectoderm (#) as noted in Rana (ef. figs. 1, 
2, 3, plate). So there is no fundamental difference, on the contrary 
agreement in every respect with what we found in Rana. 
Now in Rana we stated that the blastopore, after becoming slit- 
like, continues to move backward a small distance, approaching the 
future anus, which manifests itself in longitudinal sections in that 
the little lip which represents the ventral blastopore border becomes 
a little shorter. This now we see happening also in somewhat further 
advanced stages of the axolotl-egg: on sections the ventral lip gets 
shorter and soon, being here already small, it disappears altogether. 
In the egg shown in fig. 25 and c (text) the medullary folds are on the 
point of coalescing, except at the fore and the rear end. The blasto- 
pore still appears as a slit. The longitudinal section (fig. 6) shows 
that the ventral blastopore lip has nearly disappeared: as a result 
of the backward movement the rear end of the slit-like blastopore 
has arrived at the spot where the anus must break through! 
Especially interesting is next the egg shown in fig. 2d, where the 
medullary tube has just closed, except at the hindmost extremity, 
where the anterior part of the slit-like blastopore has just been 
overgrown by the medullary folds. Whilst in Rana the whole 
blastopore is in this way enclosed, in the axolotl the medullary folds 
leave an opening over the rear end of the blastopore, which is the 
anus (q). 
Only one egg in this stage was found by me among my material. 
This was cut into longitudinal sections. Morean studied a similar 
egg in transverse sections. I reproduce here the outline of his 
excellent figures which wholly confirm my way of presenting things. 
Fig. 3a represents a section through the medullary tube just in front 
of the blastopore. Under it the anal diverticulum has been intersected. 
The medullary folds just meet. Figs. 36 and ec show the blastopore 
in its anterior half, as is of course the case in many succeeding 
sections. The medullary folds meet over the blastopore, the latter 
