488 HENEAGE GICBES. 



The head as it appears in the fresh specimen has a diiFerent 

 refractive power to the rest of the organism, and with a 

 high power appears to be a light green colour ; there is also 

 a central line running up it, from which it appears to be 

 hollow. 



The elliptical structure at the base of the head connects 

 it with the long thread-like body, and the filament seems to 

 spring from it. 



Whilst the spermatozoon is living this filament is in con- 

 stant motion ; at first this is so quick that it is difficult to 

 see it, but as its vitality becomes impaired the motion gets 

 slower, and it is then easily perceived to be a continuous 

 waving from side to side. 



When the connecting membrane is thrown into folds as 

 the motion gets slower it is readily seen with a high power, 

 but it is only visible in the fresh specimen, and disappears 

 entirely on the application of glycerin. 



This moving filament forms a most beautiful object under 

 a moderately high power; it can be seen with Crouch's i 

 or Zeiss' D, but with Powell and Lealand's J- immersion on 

 the new formula, it is seen to perfection. 



The constant wavy motion gives one the idea that a fine 

 thread is being constantly poured out from the base of the 

 head, and it is difficult at first to realise what the motion is. 



After a large number of experiments with reagents, I 

 found that after placing the spermatozoon in a 5 per cent, 

 solution of chromate of ammonium the body and filament 

 can be stained with one reagent, while the head would take 

 another. This is best shown by staining the spermatozoon 

 first deeply with hsematoxylin, when it will be found that 

 the body and filament show the colour well, but the head 

 scarcely at all, and staining it then in a weak solution of 

 aniline blue ; if it be not left in this fluid too long the head 

 will be found a bright blue, while the body and filament 

 remain coloured with the haematoxylin. 



I have always found that the elliptical structure 

 uniting the head and body remained of the same colour 

 AS the body and filament. It is a difficult thing to do 

 this double staining well, since a slight mistake in the time 

 of immersion or in the strength of the solution alters the 

 result of the whole experiment, and although I have had 

 numberless failures, I have succeeded in so many instances 

 that I am confident the suhstance of which the head is com- 

 posed shotvs a different chemical reaction to the rest of the 

 orgajiism. 



With regard to the existence of a homogeneous membrane 



