48 



GENETICS 



transplantation of oysters show more variation in 

 their new habitat than they did in the old one with 

 respect to the particular character measured, namely, 

 the relative size of the mouth aperture compared with 

 the height of the entire shell. 1 



b. Bimodal Curves 



Sometimes two conspicuous modes make their ap- 

 pearance in a frequency polygon, as Jennings found, 



* 



Individuals 



25 - 



20 



10 



20 4- 2.8 32 36 40 44 



5 56 60 64 



FIG. 26. The body width of a population of the protozoan Paramecium\ 

 showing a polygon with two modes. A, Paramecium aurelia. B, 

 Paramecium caudatum. After Jennings. 



for example, in measuring the body width of a popu- 

 lation of the protozoan Paramecium (Fig. 26). 



1 ' ' Variation in Urosalpinx. ' ' Walter, 

 pp. 577-594. 



Amer. Nat. 1910, Vol. XLIV. 



