PLATE XL VI. 

 Effects of Pressure. 



Fig. 45. Exp. 918: Egg pressed during formation of second polar body, which is abnormally large. 



Fig. 46. Exp. 918: Egg pressed during first cleavage which was rendered unequal; nuclei abnormally 

 lobulated. 



Fia. 47. Exp. 958: Egg shaken during first cleavage. Similar to preceding. 



Fig. 48. Exp. 901: Very large yolk lobe at vegetal pole of one of the cells. 



Fig. 49. No. 724: Egg probably pressed during the first cleavage; second cleavage spindles abnormally 

 small. 



Fig. 50. Exp. 918: Pressed during second cleavage in the direction of the spindle axes; macromeres 

 A and B have divided normally giving rise to micromeres la and 16; in macromere CD the second cleavage 

 is still incomplete, and the entire amphiaster is abnormally large. 



Fig. 51. Exp. 911: Pressed during the first cleavage; three macromeres with multiple nuclei formed 

 probably as result of a triaster. 



Fig. 52. Exp. 911: Pressed during second and third cleavages in chief axis of egg; macromeres C and D 

 with their micromeres approximately normal; macromeres A and B have divided in abnormal planes 

 giving rise to macromeres 1A 1 and IB 1 instead of micromeres. 



Fig. 53. Exp. 911: Pressed during second and third cleavages in chief axis of egg; all the upper tier 

 of cells except lc are abnormally large and are dividing like micromeres of the first set; in IB 2 , 1C and ID 2 the 

 direction of division is like that in the formation of the 2d set of micromeres. 



Fig. 54. Exp. 915: Pressed during 2d and 3d cleavages in chief axis of egg; macromere A divided 

 nearly equally into 1A 1 and ll 2 , which are now forming micromeres of the 1st set; macromeres 15, 1C 

 and ID are forming micromeres of the second set. 



Fig. 55. Exp. 904: Pressed during 3d cleavage, the direction of which was changed from dexiotropic 

 to Isotropic in all quadrants except B; correspondingly the next cleavage (shown by spindles) is dexiotropic, 

 instead of Inotropic as in typical eggs. 



Fig. 56. Exp. 915: Pressed in chief axis during the 4th cleavage, the chief result being the enlarged 

 size of 2a and 2c. 



