EXPLANATION OF PLATE I. 



Fig. I. Photomicrograph of section of embryo kitten about five millimeters 



in length. 

 Fig. 2. Photomicrograph of cephalic extremity of saine section enlarged. 

 N. Nest of mesoblastic cells. 

 S. P. Seesel's pocket. 

 H. C. Hypophysis cerebri. 



I. Infundibulum. 

 P. I. Processus infundibuli. 

 A. C. V. Anterior cerebral vesicle. 

 M. C. V. Middle cerebral vesicle. 

 P. C. V. Posterior cerebral vesicle. 



