u 
Nachdruck verboten. 
Preliminary Note on the Process of Gastrulation 
in Chelonia. 
By K. Mrrsuxuri, Ph. D., Imperial University, Tokyo, Japan. 
With 8 figures. 
I have recently been studying the process of gastrulation in 
Chelonia caouana Wacr. and give below a summary of the re- 
sults at which I have arrived. At the risk of appearing dogmatic, 
I omit all the details on which my conclusions rest, and hope that 
the reader will pass judgement on them, only after the perusal of the 
full paper which will appear shortly in the Journ. of the College 
of Science, Imp. Univ. Tokyo, Japan, Vol. VI, and in which 
all the facts will be given and their bearing will be discussed more 
of length than is possible here. 
1) When segmentation has gone on for some time, there are es- 
tablished in the blastoderm two layers: (a) the superficial epiblast 
composed in the region of the embryonic shield of columnar cells and 
(b) the lower layer composed of irregular stellate cells and probably 
not forming a complete membrane (fig. 1). 
2) This separation into two layers takes place in all the parts 
of the blastoderm with the exception of a small area at the posterior 
end of the future embryo (fig. 1 Prim.- Kn.). Here there is not 
only no differentiation of the layers but a thick knob consisting of a 
reticulated mass of cells is produced by the accession of cells from 
the subjacent bed of yolk. This is the Primitive Plate or Pri- 
mitive Knob. 
3) In the middle of the primitive knob, an invagination is pro- 
duced (fig. 2 Arche). At first, it goes straight downwards but soon 
takes a forward horizontal course (fig. 3). This is the Invagination 
Cavity or the Archenteron. Its dorsal opening is the Blasto- 
pore. The archenteron extends itself gradually forwards pari passu 
with the anterior enlargement of the primitive knob. (Compare figs. 
2—3.) 
4) The roof of the archenteron which becomes continuous with 
the epiblast at the dorsal lip of the blastopore assumes a columnar 
arrangement, the process beginnning at the posterior end and pro- 
ceeding gradually forwards. From the median part of the roof are 
