2 1 2 CONKLIN. 



EXPLANATION OF PLATE II. 



Fig. 13. Completion of first quartette. Position of poles of preceding spindles 

 as indicated by asters show that division was dexiotropic. Eight cells. 



Fig. 14. Fourth cleavage, laeotropic. First quartette has rotated into furrows 

 between macromeres. 



Fig. 15. Completion of second quartette and laeotropic rotation of ectomeres. 

 Twelve cells. 



Fig. 16. Fifth cleavage. Laeotropic division of first quartette and formation 

 of "turret cells" (trochoblasts), la, ib, ic, id. 



Fig. 17. Sixth cleavage, dexiotropic. Formation of third and last quartette of 

 ectomeres. Sixteen cells. 



Fig. 18. First division of second quartette, dexiotropic. 3d has recently been 

 separated from macromere D and still shows astral radiations. Twenty cells. 



Fig. 19. " Resting stage," showing quadrangular plate of ectomeres with 

 angles of plate in furrows between macromeres. Twenty-four cells, 4 apicals, 4 

 turrets, 1 2 belt cells, and 4 macromeres. 



Fig. 20. Ectoblastic plate removed from macromeres, showing the overlapping 

 of cells. 



Fig. 21. Laeotropic division of D and formation of first member of fourth 

 quartette, the mesentoblast 4d (ME). Twenty-four cells. 



Fig. 22. Second division of first quartette (dexiotropic) and formation of basal 

 cells of cross. The spindle has not yet appeared in id. Twenty-five cells. 



Fig. 23. Complete separation of basal cells of cross (la''^ ib'-^ ic''% id'-^). 

 Twenty-nine cells. 



Fig. 24. Side view of egg of about the same stage as Fig. 23, showing the 

 relation of the mesentoblast to macromere D. 3d dividing. 



