GROUPS OF FLUCTUATING VARIATION 



563 



TABLE 1 -'■'■■ 



Time in minutes from insemination to the cell division of the first egg in Arbacia 



follows: The eggs were inseminated in sea water, and kept in 

 a water bath at the desired temperature. The eggs remained 

 in this water bath until about the time when the first segmen- 

 tation was expected to occur. In the meantime, a second water 

 bath was prepared on the stage of the microscope whose tem- 

 perature was slightly below that of the desired temperature. 

 This water bath contained the watch glass in which the segmen- 

 tation of the eggs was to be observed. The watch glass had 

 therefore the temperature at which the eggs were observed. 

 The temperature of this water bath was also kept constant. 

 When the temperature at which the latitude of variation was 

 observed was very low and that of the air of the room was high 

 a slight error crept in, in as much as the temperature of the 



THE JOURNAL OF EXPEKIMENTAI, ZOOLOGY, VOL. 19, NO. 4 



