518 



H. S. Jennings and George T. Hargitt. 



k -h i, and of C2 + i, both belonging to the aureha group, but 

 differing in mean size. 



Taking, for example, the case of A; + i, previous measurements 

 had shown the mean length of k to be about 125 microns; 

 that of i to be about 93 microns. (See table 1.) Fig. 16, k, i, 



i + k 



75 81 87 93 99 105 111 117 123 129 135 141 147 153 159 165 



Length in Microns 



Fig. 16. Polygons of variation in length for a culture in which the two aurelia 

 races i and k have been' living together for two weeks, in comparison with poly- 

 gons for each race taken separately. The broken lines are for the two separate 

 races (measurements of April 21, 1910); the continuous line shows the double 

 peaked polygon from the culture in which both are present (measurements of 

 June 13, 1910). 



(In the mixed culture the race i was more numerous than k, so that the left 

 peak, representing i, is higher than the one to the right, representing k. Fur- 

 ther, the nutritive conditions in the mixed culture were such that both races show 

 a greater mean length than in the separate cultures, thus displacing the peaks to 

 the right. 



shows polygons of variation of k and i taken separately, while 

 k -\- i shows the polygon of variation formed when the two have 

 been living in the same culture for two weeks. The two races 

 are evidently still present. They were found to persist side by 



