114 FRANK R. LILLIE. 



The results of the destruction of the head-fold of the amnion 

 in the stage of 46 hours are: (i) Inhibition of the progressive 

 differentiation of the amniotic zone of the somatopleure ; (2) 

 failure of the parts of the lateral folds left to unite around the 

 embryo. The failure of the amniotic folds to unite in the region 

 where they are best formed and are of more than sufficient length 

 for enclosure of the embryo shows that the normal union of the 

 folds is due to the guidance and support of the earlier formed 

 parts of the amnion. 



The tail-fold, however, forms in a fairly normal manner. The 

 actual abnormalities in this fold are probably secondary, that is, 

 probably due not so much to direct disturbance of the amnion 

 itself as to the freedom of movement of the embryo permitted 

 by the absence of the head-fold, resulting in the withdrawal of 

 the tail of the embryo from the forming tail -fold. 



The body-wall is unenclosed for 1 1 3 sections ; in a normal 

 embryo of about the same age the body-wall is unenclosed for 

 about 55 sections. Thus it would appear that the closure has 

 been delayed. 



Experiment 60. 



Age of the embryo at the time of operation about 33 hours. 



Operation. The blastoderm was cauterized just lateral to the 

 right optic vesicle, as in experiment 57, producing a large open- 

 ing (Fig. 14). 



The egg was reopened 72 hours after the operation, and a 

 large, finely developed vascular area was seen with apparently 

 no embryo. But more careful examination revealed the naked 

 hind quarters of an embryo sticking up near the center of the 

 vascular area, the whole trunk and head of which were plunged 

 through the blastoderm into the yolk. The head and trunk of 

 the embryo had slipped through the hole made by the operation 

 into the yolk-sac, and the edges of the blastoderm around the 

 original opening had fused in such a way as to close around the 

 hinder part of the embryo. A large part of the vascular area 

 was cut out and the embryo was gently floated into a watch 

 crystal of physiological salt solution. Turning over the blasto- 

 derm, the embryo was revealed entirely without an amnion (Fig. 

 15). Not even the tail-fold was found. 



