60 Pub. Puc/et Sound Biol. Sta. Vol. 2, No. Si 



PLATE 15 



For abbreviations see table of cell lineage. 



Fig. 15. Simultaneous laeotropic division of macromeres and first 

 quartet; 8 to 16 cells. 



Fig. 16. Sixteen cells completed. Division of first quartet not quite 

 synchronous. 



Fig. 17. Formation of dexiotropic spindles for fifth cleavage* 16 

 to 24 cells. The cleavage in the second quartet is slightly in advance of 

 that in the macromeres. 



