THE PETMITIVE STEEAK OF THE RABBIT. 221 



Fig. 35. — A transverse section through the edge of the embryonal area of 

 a specimen rather older than Fig. 4, on a level corresponding to the line 13. 

 X 175. 



Fig. 36. — A transverse section through the corresponding region of a 

 specimen like Fig. 7. X 175. 



Fig. 37. — A transverse section through the corresponding region of a 

 specimen like Fig. 9. X 175. 



Fig. 38. — A transverse section through the corresponding region of a 

 specimen rather older than Fig. 10. X 175. 



PLATE 22. 



Fig. 40. — Diagram showing lines of growth, i. e. expansion of blastodermic 

 vesicle of the embryonal area and surrounding parts of a rabbit embryo, 

 corresponding to Fig. 1, Plate 20. 



Fig. 41. — A similar diagram of a slightly later stage, corresponding to 

 Fig. 2 at the time of the first appearance of the secondary centre of growth, 

 which is placed eccentrically to the centre of the primary area of growth. 



Figs. 42, 43, 44. — Similar diagrams illustrating the increase in importance 

 of the secondary centre of growth. These correspond to Figs. 3 or 4, between 

 5 and 6, and to 8. 



Fig. 45. — A portion of a similar diagram of the posterior end only of the 

 embryonal area of a specimen, corresponding to Fig. 10, or a little later. 



