PLATE II. 



Figs. 12-18, 21, 25 ^nd 26 Beivë oiaio 

 FigS- 19 aiid 20 Bcroé J'orskiilii 

 Figs- 22, 27-30 CalUonira hialaUt. 

 FigS- 23 aiid 24 J'.xchaii'i iiiiilticoruis. 



Fig- 12- Very young cleavage-head, x 270. 



Figs- 13 and 14- Two stages of the elongation of the cleavage furrow. x270. 



Fig- 15- Cleavage-head having fused with the ectoplasm in the micromere 



region. x27Ü. 

 Figs- 16-18- Last three stages of the first division, x 27Ü. 

 Figs- 19 ai^d 20- T^^'o «tages of the first division of the egg of 7>. forskalii, drawn 



respectively at 10. t A.M. and 10.15 A M. x71. 

 Fig- 21- Early two-cell stage showing the ectoplasmic accumulation in the 



luicroiuere region. xOO. 

 Fig- 22- Early two-cell stage of CalUan'oa. Notice fenestrated cell- wall and thicker 



ectoplasm at the micromere region. x390. 

 Fig- 23- Two-cell stage of Knchnis, in which the cleavage is about to begin. 3.55 



P.M. X140. 

 Fig- 24- The same; in one of the blastomeres the second cleavage has been taking 



place. XI 40. 

 Fig- 25- Blastomere of the four-cell stage. x71. 

 F^ig- 26- Beginning of the third division. x60. 



Fig- 27- Beginning of the third division (Callianira) ; cf. Fig. 22. x390. 

 Fig- 28- Blastomere of the four-cell stage, in which the third cleavage lias more 



advanced {CdllUtnlra). x200. 

 Fig- 29- t'pper cell of the eight-cell stage, giving off a micromere towards the 



micromere pole {CaUianira) x390. 

 Fig 3D- Lower cell of the eight-cell stage giving off a micromere horizontally 



{Callianira). X390. 



