THE BIOLOGY OF THE FROG 



CHAP. 



B 



D 



G H 



FlG. 16. Segmentation of egg. (After Schultze.) A, tuo-cell stage, 

 with the beginning of the second furrow; B, eight-cell stage, showing 

 the cross furrow at the animal pole; E, eight-cell stage; C, D, F, G t 

 sixteen-cell stages, showing variations in the plan of cleavage ; //, thirty- 

 two-cell stage. (From Morgan's "Development of the Frog's Egg.") 



