PLATE 5 



EXPLANATION OF FIGURES 



43 Slightly oblique section of a twenty-seven-celled stage, showing three of 

 the four descendants of the original nucleolar blastomere. Nine hours. X 1260. 



44 Upper end of a section through a twenty-eight-celled stage, with two of 

 the sixteen polar nuclei all in mitosis. Nine hours. . X 1260. 



45 Median section of a fifty-two-celled stage. The four nucleolar cells are 

 all shown in the section. Nin teen hours. X 1200. 



46 Median section of a sixty-celled stage. Ninteen hours. X 1121. 



47 Oblique section of a seventy celled stage. It shows five of the six nucleo- 

 lar blastomeres present in the egg. Twenty six hours. X 1153. 



48 Median section of a 135 celled stage. This egg has retained to aTemark- 

 able degree the original pear shape. Forty hours. X 1035. 



