PHYSIOLOGY OF THE SPERMATOZOON 105 



this to the margin of the slide along the path in which 

 the pipette was introduced and withdrawn (cf. Fig. 

 15). The ring and linear aggregation are separated 

 from the general sperm suspension by a clear space 

 1.5 to 2 mm. in width. No such reaction takes place 

 with reference to a drop of normal sea-water. Greater 



Fig. 14. — Reaction of a sperm suspension of Nereis to a drop of 

 I per cent CO2 sea-water (natural size). The preparation (a) is mounted 

 on a slide beneath a raised cover slip, a shows the form of the reaction 

 after 15 seconds; b, 75 seconds; c, 105 seconds; d, 195 seconds. In d the 

 general suspension has aggregated. The drop to the right in a is a 

 control drop of sea-water. Note in a that the spermatozoa also with- 

 draw from the margin of the preparation, thus in the direction of 

 increasing CO2 tension. 



dilutions of the CO2 sea-water will act positively in 

 the case of fresh sperm suspensions. The ring forms 

 well within the margin of the drop in the case of 1/200 

 dilution. In case of stronger CO2 solutions the ring is 

 wider and tends to grow at the periphery as the CO2 

 diffuses outward. In general the aggregation tends to 

 occur at a place in the CO2 gradient near the point of 

 paralysis of the spermatozoa. 



