618 A. S. PARKES 



Zeleny and Faust (8) have demonstrated dimorphism of the 

 head lengths. The work recorded in this paper was an attempt 

 to extend the appHcation of this correlation to other mamma- 

 lian spermatozoa for which chromosomal dimorphism has been 

 shown. 



Methods and Material. 



The new work recorded here deals with man, the rat, the 

 cat, and the mouse. I have to thank Mrs. E. Sellars of the 

 Manchester Medical School for procuring the human material 

 for me from the Manchester Eoyal Infirmary. In the other 

 cases the material was obtained by dissection of the epididimis. 

 In each case smear slides were made, as this method has advan- 

 tages compared with using testis sections. Some difficulty 

 was at first experienced in making satisfactory smears owing 

 to the tendency for the spermatozoa to drop off. Increased 

 experience in manipulation, however, was found to surmount 

 this. By teasing out the epididimis in salt solution and fixing, 

 it was found possible to make the spermatozoa adhere without 

 using egg-albumen cement. For fixing Zenker's fluid was 

 used to start with, as recommended by Zeleny and Faust (8), 

 but finally the ordinary corrosive and aceti-solution (90 per 

 cent, saturated solution corrosive sublimate and 10 per cent, 

 glacial acetic acid) was found to be quite efficient. Various 

 stains were tried, but Delafield's haematoxylin was eventually 

 found to be by far the most satisfactory. 



The measurement of the spermatozoa was found to present 

 great difficulty, especially in the case of the rat and mouse 

 where the head-piece is sickle-shaped. This fact, together with 

 the minute size of mammalian spermatozoa, makes measure- 

 ment with an ocular micrometer almost impossible. Both 

 these difficulties were alleviated by using the Zeiss-Greil 

 drawing apparatus possessed by the department. This consists 

 of a lantern throwing light through a horizontal photo-micro- 

 scope and projecting the image on to a screen. By placing 

 a mirror at 45 degrees in front of the eye-piece the image can 

 be thrown down on to a table. This apparatus can be used 



