3ßß HIROTA; ON THE SERO-AMNIOTIC CONNECTION, 



d). The epiblaatic layers of the extra-embryonic parts are stratifi- 

 ed, at least near the connection. 



e). The connection between the serous envelope and the amnion 

 persists durino- egof-life and no direct continuity is ever made between 

 the extra-embryonic coelomic cavities of the two sides along the length 

 of the connection. 



f). The growth of the allantois is greatly influenced in later 

 stages by the presence of the sero-amniotic connection. 



Thi' essential points in which they disaijree. — a). In the chick the 

 amniotic fold arises in comparatively later stages than in Chelonia, and 

 the extra-embryonic coelomic cavity is from the first extended backwards 

 in the amniotic fold almost as far as the epiblast has progressed, while 

 in Chelonia the mesoblastic cavities insinuate themselves secondarily 

 from the two sides in the latero-median direction. It is owing to this 

 difference tliat in the amniotic fold of the chick there is found no 

 conspicuous area free from the mesoblast, and that there is no meso- 

 blastic septum in Chelonia before the epiblastic sero-anuiiotic connec- 

 tion appears. 



h). In Chelonia the epiblastic delta of the amniotic fold is 

 a.lwavs larger than that of the chick, but in the latter it is enormously 

 thickened dorso-Aentrally. 



c). In Chelonia the anuiicjtic fold passes over the tail end before 

 the lattei- is yet differentiated and there is therefore formed no proj»er 

 tail fold. In the chick, the head and tail folds fuse together at the 

 ]e\ el of the rudimentary right hind limb and therefore there is pro- 

 duced no trace of the posterior tube, which forms so (conspicuous a 

 feature of the chelonian amnion. 



d). The epiblastic bridge of the connection seems to be persistent 

 in Chelonia, while in the chick it is replaced by mesoblast and becomes 

 extended on both sides. 



