BiOBLOw. — Development of Lepas. 



PLATE 3. 



All Figures drawn from sections. 



Fig. 23. Early anaphase of first cleavage. 



Fig. 24. Late anaphase. Dividing egg in rotation. Second polar cell in cleavage 



furrow. 

 Fig. 25. Telophase of egg, which has not yet rotated tlirough a complete quadrant. 

 Fig. 26. Rotation completed. Cleavage plane developing. Spindle disappearing. 



Chromosomes vesicular. 

 Fig. 27. Two-cell stage. Vesicular chromosomes unite to form the nuclei. Yolk 



has approached the vegetative pole, as in Figure 16. 

 Fig. 28. Second cleavage at beginning of metaphase, viewed from animal pole. 

 Fig. 29. Equatorial-plate stage of second cleavage; same egg as Figure 28. 



Lateral view. 

 Fig. 30. Second cleavage in late anaphase, viewed from animal pole. /, /, indi- 

 cate first cleavage plane, //, //, second cleavage plane. 



The long arrow falls in the projection of the sagittal plane of the 



embryo. 



