GROUPS OF FLUCTUATING VARIATION 



TABLE 5 

 Temperature coefficients for latitude of variation 



567 



temperature in the watch glass may have risen shghtly during 

 the observations. Since in the determination of the temperature 

 coefficient the value for the low temperature forms the numer- 

 ator, it is obvious that the observed temperature coefficients 

 are liable to be a little smaller than they would be without this 

 error. We expect to test this idea next season. 



THEORETICAL REMARKS 



It was found in a previous investigation that the time which 

 elapses from the moment of insemination to the moment of the 

 beginning of cell division in the egg of Arbacia, is a constant 

 for a given temperature. On the basis of the enzyme theory 

 this was to be explained on the assumption that the mass of 

 ferments contained in the egg of the sea urchin responsible for 

 this process is approximately constant in each individual egg. 

 This would mean that the hereditary factor determining the 

 rate of cell division consists in determiners for definite quantities 

 of ferments. This idea was put to a test by applying it to the 

 fluctuating variability of this process. While for a given tem- 

 perature the eggs of x4.rbacia will always begin to segment at the 

 same time, not all the eggs segment simultaneously. Assuming 



