88 



OTTO GLASER. 



The data from female C, treated similarly, give curve C. 



CURVE C. Diameters of 100 eggs from one specimen of Arbacia punctulata. 



Since the diameters for females B and C on the average are 

 equal, the eggs of these two may be considered as homogeneous 

 material. If this is done, then after the usual statistical sim- 

 plifications, 1 an almost symmetrical curve results. 



50- 

 40- 

 30- 

 20- 

 10- 



57 60 



65 



70 



75 



80 



85 



90 



100 



105 107 



CURVE BC. A composite of the diameters of 200 eggs from two specimens .of Arbacia punctulata. 



COMPARISON OF UNFERTILIZED AND FERTILIZED OVA. 



The variability exhibited by these eggs and the differences in 

 range between different females, show clearly that if one wishes 

 to make trustworthy comparisons between the volumes of 

 unfertilized and fertilized ova, it is either necessary to use a 

 large number of each kind from a single female or to deal with a 

 smaller number and measure the identical eggs before and at\er 

 fertilization. 



Before adopting the second alternative, I made a series of 

 tracings of unfertilized and fertilized ova to see whether measure- 

 able differences really existed. The results, averaged, were as 

 follows : 



Unfertilized eggs; 77 measurements; average diameter, 74.1 micra. 

 Fertilized eggs; 91 measurements; average diameter, 70.7 micra. 



Loss 3.4 micra. 



1 The eggs are treated in sets of three, and average diameters not more than 

 three micra apart are considered as belonging to the same group. 



