158 



A. n. UEOINALD riULLER. 



little of tlie thick white sperm-fluid in it by means of a pipette, 

 a peculiai- effect may be ob-servcil as a result of the presence 

 of an air-bubble. The spermatozoa, in incredible numbers 

 and constantly colliding, iirst swarm equally well all over 

 the ])reparation. After about five minutes one sees macro- 

 scopically, when looking ut the slide upon the microscope 

 stage, a black zone arise about 1 njm. from the edge of the 

 air-bubble. Ou examination with the microscope one sees 

 that there are fewer spermatozoa there than anywhere else. 

 Three zones (Fig. 2) niay then be made out around the air- 

 bubble z : a, an inner zone crowded with actively motile sper- 

 matozoa ; 6, a much thinner zone (that appearing macro- 



CL 



:. ••■.■/.•.'.• ?c 





Figs. 2 ami 3. 



scopically black) in which thei-e are compai-atively very few 

 spermatozoa; and c, the zone outside h (which extends over 

 the rest of the preparation nearly to the edge of the cover- 

 glass) where the spermatozoa ai-e crowded, so far as I could 

 judge, about as thickly as in zone <(, but have all come to rest 

 from want of oxygen. As one watches the preparation one 

 sees (fig. 3) that the spermatozoa gradually leave the zone a 

 and collect on the inner edge of the zone c, upon reaching 

 which they cease to move. A ring of thickly placed, dead 

 spermatozoa thus arises. A similar collection of dead sper- 

 matozoa also takes place about 1 mm. from the edge of the 

 cover-glass. The explanation of this curious ])henomeuun, 



