ORGANS IN THE EMBRYO OF THE FOWL. 



I I I 



the embryo, but towards the dorsal surface ; the flexures were 

 normal. The striking thing was the apparent entire absence of 

 the amnion ; the embryo lay naked on the surface of the blasto- 

 derm, to which it was attached, in the same manner as a selachian 

 embryo by a very broad somatic and splanchnic umbilicus. 



In the normal embryo of this age the amnion is completely 

 closed, and the body-wall of the embryo has, therefore, lost all 

 connection with the chorion. 



FIG. II. Experiment 36. Operation diagram. Outline of embryo of chick of 

 about 46 hours, after Duval. The ruled area shows the site of the operation with the 

 heated needle. For description of the operation see text. 



This embryo was cut into 625 transverse sections. These 

 confirm the general absence of the amnion, and at the same time 

 furnish additional data. Back to about the 354th section (forty 

 sections behind the heart), the somatopleure beneath the embryo 

 is entirely missing ; evidently it had been torn away by the 

 operation and had not been replaced. Throughout this region 

 the extra-embryonic somatopleure begins on each side of the 

 embryo with a free edge. A short distance behind the heart, 

 folded portions of the original amnion appear lying in the gap in 

 the somatopleure, and continuous with the midventral line of the 

 body- wall. Beginning with about the 3/ist section (see Fig. 

 13) the body wall is open ventrally, and is continuous with the 



