EARLY DEVELOPMENT OF RANA TEMPORARIA. 127 
gut of Gotte: not only is this the case, but the blastopore also 
is situated in precisely the same position in which, according 
to him, the proctodeeum is being formed. 
May it not thus be possible that what Gotte calls the post- 
anal gut, and which, according to him, closes up after forma- 
tion of the proctodzum, is in reality the posterior part of the 
neural canal which in early stages opened into the blastopore, 
but which, later on, disappeared ? 
It is further rather difficult perhaps to say whether, strictly 
speaking, a neurenteric canal is present in Rana, as this term 
is usually used in connection with the enclosure of the blasto- 
pore, and when this itself forms a means of communication 
between the alimentary and neural canal. Perhaps, however, 
the term “ neurenteric canal ”’ may be applied to all structures 
which allow of communication between the two canals, and 
which itself, in subsequent development, closes up and dis- 
appears: using the term in this sense one is clearly present 
and well developed in Rana. 
(2) Some Points ConnEecTED witH THE Harty DeEvetor- 
MENT OF THE CRANIAL NERVES. : 
The following are a few notes connected with the early 
development of the cranial nerves of the Amphibia, and I must 
acknowledge my indebtedness to Professor Marshall for kind 
assistance, and for his permission to use the laboratory and 
materials of the Owens College. 
Sections of eggs of Rana as early as the close of segmenta- 
tion show that the epiblast is formed of two distinct layers of 
cells, the outer of which is one cell deep, whilst the inner 
varies much in thickness in different parts and continues to do 
so during development. 
Of these the first is the epidermic and the second the nervous 
layer, and the development of the whole of the nervous system, 
save the lining of the neural canal, is concerned solely with 
the latter. 
On what will ultimately be the dorsal surface of the embryo 
