PLATE 3 



EXPLANATION OF FIGURES 



32 Eight-cell stage, ventral view. 



33 Eight-cell stage, dorsal view; the ectomeres are above instead of anterior 

 to the parent cells as in figure 32. 



34 Early nine-cell stage, upper pole (dorsal view). 



35 Late nine-cell stage, ventral view. 

 36-37 Ten-cell stage, ventral and right sides. 



38 Sixteen-cell stage, ventral view; the embryo is extended in an antero- 

 posterior direction. 



39 and 40 Sixteen-cell stage, the left side ; D side is dorsal and dorso-posterior. 



41 Sixteen-cell stage, right side. 



42 Sixteen-cell stage, ventral view; all of the cells are represented; note the 

 shape of the cells. 



43 and 44 Sixteen-cell stage, dorsal view; the D derivatives are considerably 

 elongaged transversely. 



45 Nineteen-cell stage, right side; dS d-, d^-^ having divided; the eggs at 

 this stage are transparent and the position of all the cells can be recognized. 



46 Twenty-cell stage, right side; the extra cell is d^ from D; the formation 

 of d" is unusual. 



47 Twenty -nine-cell stage, upper view; a continuation of figure 46 during the 

 fifth cleavage; the A row of cells has not divided. 



428 



