u8 



FRANK R. LILI.IE. 



plicated by conditions that do not properly belong to the subject 

 of this paper. There is but one uncomplicated case (exp. 18). 

 In this experiment the hind-end of the embryo was cauterized 

 immediately after the appearance of the tail-bud (Fig. 17), thus 



FIG. 17. Experiment 18, operation diagram. Outline of embryo of chick of 

 about 52 hours, after Duval. The ruled area represents the part destroyed by the 

 heated needle. 



destroying the tail-fold of the amnion. When the egg was re- 

 opened forty-eight hours later, a well-developed embryo of about 

 five days was found in which the amnion ceased with a free edge 

 immediately in front of the hind-limbs (Fig. 18). 



The conditions of the membranes in this embryo are other- 

 wise very complicated and difficult to understand. Thus there is 

 in addition to the amnion a fold of the blastoderm surrounding 

 both amnion and embryo (Fig. 18). In the posterior half of the 

 embryo the body-wall is directly continuous with the wall of the 

 intestine as in 60. As this embryo will come up for description 

 elsewhere, I shall not dwell further on this topic. 



The fact that stands out distinctly is that the tail-fold of the 

 amnion has not regenerated and that the head-fold has not 

 compensated for the absence of the tail-fold by continuing its 

 growth backwards. However, I have a number of embryos in 





