622 



A. S. PARKES 



Table II. Frequency of Head Lengths of Spermatozoa 

 OF Rat. 



2 -as -J 35 -A vl.5 -3 '55 -6 ■65 1 TS -3 -83 •<» <!S l,-0 OS -I 



Frequency po'ygon of head lengths of spermatozoa of rat. 



Von Winiwarter (3) has shown that the spermatozoa of the 

 cat are cytologically dimorphic, one type having eighteen 

 chromosomes and tlie other seventeen. In measuring the 

 head lengths, however, no clear dimorphism was fomid. The 

 results were as follows : 



