SEGMENTATION OF THE EGG OF BDELLOSTOMA STOUTl 



PLATE I 



Fig. 1 . Lateral view of germinal hillock showing first cleavage furrow. 



Fig. 2. Polar view of first cleavage furrow, early stage. 



Fig. 3. Polar view of later first cleavage with furrow broad and shallow at ends. 



Fig. 4. Lateral view of germinal hillock in second cleavage. Note change in height and width 



compared with Fig. L 

 Fig. 5. Polar view of early four-celled stage. 

 Fig. 6. Polar view of later four-celled stage, showing depression at intersection of furrows and 



widenings at their outer ends. 

 Fig. 7- Lateral view of germinal hillock in late four-celled stage. Note the rounded dome-shape of the 



germinal hillock. 

 Fig. 8. Polar view of the same blastodisc in late four-celled stage. Note the large intercellular space 



at the intersection of the furrows. 

 Fig. 9. Polar view of unique four-celled blastodisc. 

 Fig. 10. Polar view of slightly irregular four-celled stage, showing depression at the intersection of 



furrows. 

 Fig. IL Polar view of an egg in four-celled stage in which the second cleavage furrows do not meet. 

 Fig. 12. Polar view of a blastodisc m four-celled stage, showing the same variation m cleavage pattern 



as in the proceeding figure. 



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