526 



H. S. Jennings and George T. Hargitt. 



at middle are the actual means for the entire number, while the 

 other breadths are calculated from the mean breadth at the middle 

 by use of the ratios given in table 3. If now we construct figures 

 with these dimensions, we have in fig. 19 the typical forms and 



L2 



Fig. 19. Characteristic differences in form between caudatum (L2) and aurelia 

 {k) when living together in the same medium. The forms and sizes shown are the 

 averages from twenty-five specimens of each. X shows the form of k (aurelia) 

 when magnified to the same size as the caudatum race. Note the greater breadth 

 and different form of the posterior part of the body in aurelia. The magnifica- 

 tion (for L2 and A;) is 375. 



sizes of the races L^ and k when living together under the condi- 

 tions of the culture studied. Fig 19 also gives at X the form and 

 proportions of k as it would be if it were magnified till the length 

 was the same as for L^; comparison of this with L^ brings out 

 clearly the differences in form. 



