222 



HELEN DEAN KING. 



S. C. 





FIG. I. Part of a section of an egg that was subjected to a temperature of 34-35C. for one-half of an hour before cleavage began. 



FIG. 2. A section of an egg that was exposed to a temperature of 35-36 C. for three quarters of an hour when it was 



in the two-cell stage. S. C., segmentation cavity. 



FIG. 3. A section of an egg that was subjected to a temperature oi 33-35 C. for two hours after the first cleavage plane had 

 appeared. 



FIG. 4. A section of an egg that was subjected to a temperature of 31-33 C. for three and one-half hours when it was in the 

 32-64-cell stage of development. Bl. blastopore. 



