No. 587] 



VARIABILITY AND AMPHIMIXIS 



675 



This conclusion was based on measurements of length and 

 diameter, the volume not being computed. When this is 

 done as shown in the accompanying table (Table XI) by 



TABLE XI 



utilizing the formula V = l/Md 2 , thus allowing for slight 

 decreases in diameters, the facts present a different in- 

 terpretation. 



Three {a, b, c) of the four experiments dealing with a 

 "pure race" of P. aurelia indicate that the progeny of 

 the non-conjugants become larger, even when as a group 

 they are smaller (a, fc?) at the beginning of the experi- 

 ment. While the fourth {d) indicates a reverse condi- 

 tion so far as the measurements of October 30 are con- 

 cerned, the measurements of the sixth and seventh genera- 

 tions immediately preceding, demonstrate that the non- 

 conjugants were larger. The result on October 30, where 

 the non-conjugants became smaller, may have depended 



