STRUCTURE OF THE VERTEBRATE SPERMATOZOON. 489 



connecting the filament to the body, this membrane at 

 first seemed doubtful, and the filament appeared to be un- 

 connected with the body ; but with a high power the mem- 

 brane can be recognised in the fresh stale, and it will 

 invariably he found that when the spermatozoon is curved, 

 as it frequently is, and often lying in a double curve, the 

 filament will always be found placed at a certain distance 

 from the convexity of each curve ; this distance varies a little 

 in individual cases. 



If, while examining a specimen in salt solution or distilled 

 water, gentle pressure with the point of a needle be applied 

 to the cover-glass so as to cause a slight vibration in the fluid, 

 the filament will be seen to move to and fro but can never 

 be forced further from the body than its natural distance, 

 unless it has in any way been subjected to sufficient force to 

 rupture the membrane, in which case it may be seen lying 

 quite away from the organism to which it belongs. This 

 seldom happens, and never when the experiment is care- 

 fully done. This would not be the case if the filament 

 were free. 



In the spermatozoa of Triton cristatiis and also Salaman- 

 dra maculata, prepared with a 5 part, solution of chromate 

 of ammonium, and stained in picro-carmine, this membrane 

 is not easily seen, and the filament appears as if free of 

 the body, and twisted more or less like a spiral round the 

 latter. 



This appearance was originally described by Dr. Klein 

 in this Journal, and its more minute examination was 

 the primary object of my inquiry, which I carried on 

 under his direction. Leydig (' Lehrbuch der Histologic^) 

 describes and figures (p. 49o) the spermatozoon of Salaman- 

 drinee as if possessed of a narrow undulating membrane 

 attached to its body. 



I next proceeded to examine some of the Mammalian 

 spermatozoa to see if they possessed the filament just de- 

 scribed, and in every instance I have found it. I have 

 examined spermatozoa of horse, dog, bull, cat, rabbit, and 

 guinea-pig, and in every case the above filament was found 

 to exist. 



The structure of the spermatozoon, as is well known, is in 

 these instances slightly different from that of the sperma- 

 tozoon of Amphibian animals. The long-pointed head is 

 wanting, and the long filament does not seem to extend so 

 far as in the Amphibia, but the Mammalian spermatozoon 

 being so very much smaller it is very difficult to make out 

 the filament in its whole extent. I have seen it best in the 



