Head Length Dimorphism of Mammalian 

 Spermatozoa. 



By 

 A. S. Parkes, B.A. (Cantab,), Ph.D., 



Department of Zoology, University of Manchester. 



With 3 Text-figures. 



Contents. 



1. Introductory ..... 



2. Methods and Material 



3. Spermatozoa of Man, Rat, Cat, and Mouse 



4. Conclusion ...... 



5. Summary ...... 



6. Bibliography ..... 



PAGE 



617 

 618 

 621 

 623 

 624 

 625 



Introductory. 



Work on mammalian spermatogenesis has in a large nunlber 

 of cases shown that the spermatozoa are of two types, one 

 type possessing the accessory chromosome, whilst the other 

 type has no sex chromosome or a mere vestigal complement. 

 As the spermatozoon head is constituted almost entirely of 

 nucleus it might be expected that the additional chromatin 

 possessed by the one type would slightly increase the size 

 of the head. In three cases this correlation has been found. 

 Wodsedalek (5 and 6) has shown that in the horse and bull 

 the spermatozoa are of two types, and that in each case a 

 frequency polygon of the head lengths shows distinct 

 dimorphism. In the case of the dog, Malone (2) found an 

 unpaired accessory chromosome in spermatogenesis, and 



