I 12 



FRANK R. LILLIE. 



extra-embryonic somatopleure on one side, while on the other 

 the original gap in the somatopleure is still open (see Fig. 13). 

 In this region, the somatopleure for some distance external to 



FIG. 12. Experiment 36. Surface view of embryo ; upper surface of blastoderm. 

 The embryo is anamniote, except for a rudimentary tail-fold, all., allantois ; /. , pel- 

 lucid area. A-B, plane of section shown in Fig. 13 ; /. , fold of somatopleure. 



the part destined for the body-wall is thrown on both sides into 

 irregular folds that obviously represent the lateral amniotic 

 folds. They rapidly decrease in size posteriorly, and almost 

 completely disappear in the region extending from^the 42Oth sec- 

 tion back, /. c., a short distance back of the fore-limbs. Begin- 

 ning opposite the hind-limbs the folds again increase in size. 

 They are very irregular and do not form the normal investment 



