STEUCTURE AND DEVELOPMENTAL RATE 



149 



In lots Bi and Ci the eggs had divided once during the last 24 hours 

 and were now almost all in the 8- and 16-cell stages, while a few were 

 irregular 32-cell stages. Much cellular disorganization had taken place 

 and the cell groups were broken and irregular, often with large unseg- 

 mented protoplasmic masses. 



Lot B2 were in somewhat similar conditions, all showed more or less 

 irregular 8- and 16-cell masses. Many also showed large unsegmented 

 protoplasmic areas with a few cells around the periphery (fig. 10). 



Lot B3 at 9°C. were all developing somewhat faster than the above, 

 and now presented well-arranged high-segmentation caps. They were 

 normal in appearance up to this tune. 



When 4 days old, the control showed a perfect condition with not 

 one egg having failed to develop. There- was a vigorous heart beat and a 



Fig. 9 A cell group 24 hours old, having been in a temperature of 5°C. since 

 three hours after fertilization. The 8-cells are peculiarly arranged into two 

 groups of 4 each, such specimens may give rise to ordinary single individuals. 



Fig. 10 A large unsegmented protoplasmic mass with blastomeres around 

 the periphery. A frequent specimen in lot B2, experiment 902, when 46 hours old 

 after 43 hours at 7 °C. 



good circulation fully established. They were thus developing consid- 

 erably faster at this time of the season than did the control of experi- 

 ment 901, which was fertilized 10 days earher. These 901 embryos 

 had not developed a heart beat or established a circulation when 4 

 days old. 



Lot Bi, after 4 days at 5°C., showed a few regular cleavage caps of 

 about 64 cells. The majority, however, exhibited very irregular 

 cleavage arrangements and some were almost amorphous protoplasmic 

 masses, although all were translucent and alive. The eggs had, there- 

 fore, developed at an extremely slow rate, but had not completely 

 stopped. These specimens were now placed at room temperature. 



In lot Ci the majority had, after 4 days at 5°C., rather regular 

 64- or 128-cell caps. This lot was from a different group of eggs 

 than the B series, and its control was going in a manner exactly similar 



