38 LIBBIE H. HYMAN. 



PLATE III. 



FIGS. 45 TO 49. Embryo of about two days incubation, with general double 

 gradient, showing also high susceptibility of the eye and ear and of the region 

 involved in the turning of the embryo. 



FIG. 48. Abnormal chick resulting from retarded incubation. The anterior 

 part is normal (except the heart), but the posterior end is retarded as shown by 

 decreased number of somites on the left side, poor development of the neural 

 folds, and large mass of cells terminating the embryo, due to inhibition of the 

 growing region of the primitive streak. 



FIG. 49. Typical case of "omphalocephalic" abnormality, due to delayed 

 incubation. Posterior part nearly normal, but head reduced to a crumpled mass 

 with heart anterior to the head. 



