Figs. 9 and 10. Diagrams of Frog's Eggs Showing the 

 Probable Relations of the Axes of the Egg to the Axes and 

 Principal Organs of the Embryo. All eggs viewed from right 

 side, polar bodies above; A anterior, P posterior, D dorsal, 

 V ventral, s spermatozoon, N sperm nucleus, $IV egg nucleus, 

 m mesodermal crescent where mesoderm will form, c and n 

 gray crescent, where chorda (c) and nervous system («) will 

 form, en area of endoderm, pigmented area around polar bodies 

 will form ectoderm of skin, sc segmentation cavity, bp blasto- 

 pore, E enteron, M region of mouth. 



