INGALLS. 



PLATE 4. 



I. I>orsal and slightly lateral view of model. X 100. Reduced. On the left the body stalk is cut across. 



'1. Left lateral view of model. X 100. Reduced. On the right the hody-slalk, cut in the plane of the sections, shows 

 a large vessel; running downward and forward, also in the plane of the sections, a small portion of the amnion 



has been left. In the embryonic disc are seen the irregular ectodermic folds, its anterior extremity is undermi 1. 



The irregularity in the anterior part of the yolk-sac is due to a tear. The upper part of the model has heen 

 separated from the lower ]>y sawing through it parallel with the blastoderm; it is this upper piece which is 

 represented in Fig. 1. 



