560 



CHARLES R. STOCKARD 



Fig. 26 Outline of the yolk vascular condition in the head region of a 67 hour 

 embryo. Blood is circulating freely in the large vessel but the yolk net of ves- 

 sels is not yet connected with the current. Early black and brown chromato- 

 phores are also shown. 



Fig. 27 An isolated endothelial cavity with solid projecting tips, no con- 

 nection can be seen with any other vascular spaces. From an embryo of 90 hours. 



