914 
find in sections under the ventral lip, just as under the dorsal one, 
an archenterie slit or cavity. Not, that this archenteric cavity under 
the dorsal lip owes its existence solely to the overgrowth of the yolk 
by the dorsal lip. In this case the cavity would not reach further 
forward than the place where this dorsal lip appeared first. As a matter 
of fact, however, it soon reaches considerably further forward, so that 
doubtless also an active enlargement of the archenteric cavity by 
dehiscence of the entoderm cells occurs, though it seems to me less 
suitable to assume a sharp demarcation of the parts of the archenteron 
formed in these two manners, and to distinguish these as archenteron 
and metenteron, as ASsHETON*) did. Only by the overgrowth of the 
ventral blastoporic lip however, should there be formed already an 
archenteric cavity or slit under it, reaching to the place of its first 
pl. 
bl. 
Fig. 9, Sagittal section of a gastrula of Rana escu- 
lenta. h. pl. cerebral plate, arch, archenteron, 
bl. blastopore with yolk plug 
appearance. This now proves not to be the case, as shown in fig. 9; 
only a short slit is present under the ventral lip, not nearly reaching 
up to where this lip. first appeared. So the conclusion must be 
drawn that not only the ventral blastopore lip, but also the whole 
entoderm area in front of it performs a wandering to: the dorsal 
side, and that accordingly the entoderm is not only overgrown by 
the dorsal blastoporie lip in a backward direction, but also actively 
wanders forward to disappear under it. This reminds us of the 
controversy between. Roux and Scrurtze, mentioned in my former 
1) R. AssHETON, 1909, Professor Husrecut’s Paper on the Karly Ontogenetic 
Phenomena in Mammals. Quart. Journ. Vol. 54.- 
