I IO FRANK K. 1. 1 LI. IE. 



growth of the amniotic rudiments. The height of the fold on 

 the uninjured side is a measure of the power of independent 

 elevation of a single amniotic fold. 



On the other hand the existence of the ectamnion on the right 

 side, though in a rudimentary state, and the differences in finer 

 structure of the somatopleure on the two sides of this line in- 

 dicate that the distinction between amniogenous and choriog- 

 enous somatopleure is attained by the normal development of 

 the somatopleure as a whole, and not simply as a result of their 

 separation after fusion. However, the relatively rudimentary 

 condition of the ectamnion on the injured side shows that the 

 earlier stimulate the growth of the latter formed parts ; otherwise 

 we should expect to find the ectamnion equally developed on 

 both sides. The ectamnion of the right side does not exactly 

 join the tail-fold. 



Tail-fold. - - The tail-fold of the amnion may be well seen in 

 Fig. 8. So far from compensating in any way for the absence of 

 head and lateral folds, it is of even less than its normal extent, a 

 fact indicating (possibly) that normally its growth is stimulated 

 by the traction of the anterior section of the amnion. 



Experiment No. 36. 



Age of the embryo at the time of operation forty-six hours 

 (Duval). 



Operation. - - The operation consisted in the insertion of a heated 

 needle just in front of the heart (see Fig. 1 1). Examination of the 

 sections of the resulting embryo shows that the injury involved the 

 left optic cup slightly, and that the head-fold of the amnion which 

 extends back beyond the heart at this stage, stuck to the needle 

 and was stripped off, carrying with it a certain amount of the ad- 

 jacent somatopleure. This was not observed at the time of the 

 operation, but the conclusion is rendered positive by the subse- 

 quent examination of the embryo. 



Examination of the Resulting Embryo. 



The egg was reopened and the embryo preserved forty-eight 

 hours after the operation. The embryo (Fig. 12) appeared like 

 a normal embryo of about the ninety-sixth hour. The limb- 

 buds were well started, and the allantois extended out beyond 



