DIMORPHISM IN SPERMATOZOA OF ANASA. 



299 



They amounted to 5.22 per cent, of the total number measured. 

 Such a per cent, is not sufficient to affect the dimorphic character 

 of the curve, even if it represented spermatozoa all of a critical 

 length, i. e., 29.16^. 



Length in M. 22.68 23.76 24.84 25.92 27.00 28.08 29.16 30.24 31.32 32.40 33.48 34-56 35-64 



FIG. 13. Bimodal curve of variability of chromatic-rod length for 4r and 4! 

 combined. Number of spermatozoa around upper mode, M", is greater. 



Four hundred individuals from il, chosen at random, were 

 measured. This curve also shows a clear dimorphism. It is 

 plotted in Fig. 3. 



Preparations 2r and 2\. Of the right testis 2r, four hundred 

 eighty individuals were measured; of the left testis 2l, four 

 hundred individuals were measured. The plots of these curves, 

 Figs. 5 and 6, show that they are strikingly similar to those of 



