PLATE XLVI. 



Effects of Pressure. 



Fig. 45. 



polar body, which is abnormally 



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



lobulated 



Fig. 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 \c are abnormally large and are dividing like micromeres of the first set; in IB*, 1C and ID* 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 IA 1 and \A 

 and ID are forming micromeres 



are now forming micromeres 



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

 lseotropic in all quadrants except B ; correspondingly the next cleavage (shown 1 



as in typical 



Fig. 56. Exp 

 of la and 2c. 



