DEVELOPMENT OF THE FROG S EGG. 



307 



of the embryo projected from the trunk at approximately a right 

 angle. Consequently the neural tube is sectioned in the head 

 region parallel to its long axis, but in the trunk region at right 

 angles to its long axis. In Fig. 14, for instance, the head end 

 of the embryo projects to the right. The walls of the brain 



FIG. 15. 



vesicle demonstrate no abnormal features. Because of a certain 

 amount of twisting of this extremity but little of the pharynx 

 appears in the section upon the ventral aspect of the brain stem. 

 At the left extremity of the neural tube an almost perfect tran- 



FIG. 16. 



section of the cephalic end of the cord is shown. The notochord 

 with the transected enteron and the yolk-cell mass are repre- 

 sented immediately ventral to the tube. In Fig. 15, the cephalic 



