IO6 FRANK K. L1LLIE. 



also inadvertently torn just back of the embryo, and this opening 

 also appears in Figs. 8 and 9. This, however, was without any 

 noticeable effect on the subsequent development. 



FIG. 7. Experiment 57. Operation diagram. Outline of embryo of chick 01 

 about 33 hours, after Duval. The ruled area to the right of the head indicates the 

 area of the blastoderm destroyed by the heated needle. 



Examination of the Resulting' Embryo. The egg was reopened 

 48 hours after the operation. The heart was beating vigorously ; 

 the hole made in the blastoderm by the operation had not closed, 

 and a good deal of yolk had escaped through this and overlay the 

 blastoderm. The embryo was well developed, corresponding to 

 the stage of 70-80 hours (Duval), and apparently normal in all 

 essential respects. (A defect in the right eye was evidently a v 

 direct result of the operation.) The head of the embryo had 

 slipped through the hole in the blastoderm and was suspended 

 in the yolk (Figs. 8 and 9). 



The embryo was cut into 250 sections of 1 5 // thickness. 

 Around the edges of the opening made by the operation the 

 somatopleure turns over and becomes continuous with the 

 splanchnopleure, ectoderm with entoderm, and mesoderm with 



