ILLUSTRATIONS 



THE DEVELOPMENT OF THE FROG 



FIGURE 



GUKE 



1. Early Stages in the Development of the Frog 



Embryo. (After Parker and Haswell). 



Frontispiece 



2. Egg of Starfish. (After Gegenbaur) . . 6 



3. Ovarian Egg of Frog 7 



4. Various Stages in the Development of the 



Frog. (After Brehm from Marshall) 



5. Vertical Sections of Segmenting Eggs . . 19 



6. Sections of Three Stages of Segmentation of 



the Frog's Egg . . . 20 



7. Longitudinal Vertical Section of a Frog Em- 



bryo, Showing Commencing Invagination. 

 (After Marshall) . . . .22 



8. Longitudinal Vertical Section of a Frog Em- 



bryo at a Later Stage in the Formation of 



the Mesenteron. (After Marshall) . . 23 



9. Longitudinal Vertical Section through a Frog 



Embryo, Showing the Completion of the 

 Mesenteron. (After Marshall) . . 26 



10. Transverse Section through the Middle of a 

 Frog Embryo, at about the Stage Repre- 

 sented in Fig. 9. (After Marshall) . .27 

 xi 



