56 Pub. Piiget Soiirid Biol. Sta. Vol. '2, No. 8 1 



PLATE 13 



For abbreviations see table of cell lineage. 



Fig. 6. Resting 2-celled stage immediately following cleavage. 



Fig. 7. Resting 2-celled stage a little later than that in figure 6. The 

 cells have begun to flatten against each other and the vv'hole egg to become 

 more compact. 



Fig. 8. Formation of the spindles for the second cleavage showing 

 the slight lead of CD. The left end of each spindle lies higher than the 

 right, indicating laeotropic cleavage. 



Fig. 9. Completed 4-celled stage, showing the overlapping of A and 

 C over B and D. 



Fig. 10. Same stage as Fig. 9 seen from the side. All four cells 

 touching the same plane at their highest and their lowest points. 



