264 



K. MITSUKURI. 



ing- Ins second article, I have again gone through the chelonian emhryos 

 in my possession in order to examine this point. Tn Chelonia 

 caonana, the two youngest embryos whicli I possess (i-eferred t(^ on p. 

 ioG) are not prol):iblv much older than that corresponding to Will's figs. 

 1 and 13 (II Art.) but neither in the sketches I liad made of surface views, 

 nor in the sections, was I able to detect any structure resembling the 

 sickle. In T r i o n }' x , I vva snot mcore successful . lUit in C 1 e m m y s 

 japonica, some eml^i-yos which 1 had taken out of the ovi(hict 

 siiowed a structure wln<'h on surface views looked very much like a 

 sickle. 



Tlie annexed tigure (Fig. A.) represents one of these in which the 

 sickle is seen to extend to the sides more than in the others. This stage is 

 7nor(' ^d^'arl(vd than that in which Will figures a sickle, (Fig. 1, If 



Art.) inasmuch as the 

 invagination cavity has 

 a I read V l)roken through 

 below. On cutting sec- 

 tions of this embryo, the 

 sickle was found to be 

 due to an ac(-umulation 

 ;:,-: (^f the lower Layer cells 



continuous with the pri- 

 mitive plate. (See Fig. 

 B.). The epiblast is 

 '^^ " shar})ly marked off from 



1^ this mass, so that it can 



: not be regarded as a part 



of the primitive plate — at 

 ï'ig- A. least not in this stage. 



Ventral View of a Clemmys Embryo taken from the Oviduct. A ffpv })eC(^mino' familiar 



C5 



