528 FRANK R. LILLIE 



dilution, and some samples of sperm will exhibit slight movements 

 in it. 



In 0.75 per cent CO2 sea-water no aggregations take place, 

 but the spermatozoa move feebly. 



In 0.5 per cent CO 2 sea-water aggregations usually form slowly, 

 but the activity is usually less than the control. 



In 0.33 per cent CO2 sea-water there is apparently no inhibition 

 of activity as compared with the control. 



Whether lower dilutions stimulate more than normal sea-water 

 is difficult to say by the method used here. But the chemotaxis 

 experiments possibly indicate stimulation at a certain optimum 

 (see p. 535). 



The sensitiveness of Nereis spermatozoa to CO 2 is thus surpris- 

 ingly great, and it operates within very narrow limits. This is 

 the more surprising when comparison is made with spermatozoa 

 of other species. Thus I ascertained that the sperm of Loligo will 

 move, though feebly, in 50 per cent C02-charged sea-water, and 

 that it is very active in 20 per cent, though less so than in normal 

 sea-water. In the case of Chaetopterus it requires about 33 1 

 per cent to 40 per cent of the CO 2 sea-water to completely para- 

 lyze all the spermatozoa, though 10 per cent inhibits considerably. 

 Arbacia sperm on the other hand is much more sensitive to CO 2, 

 being completely paralyzed in 3 per cent. But Nereis is very 

 much more sensitive than any of these, and this involves some 

 very interesting forms of behavior described later on. 



b. Sensitiveness of spermatozoa of Nereis to alkalis. Alkalis 

 above a certain concentration agglutinate the spermatozoa of 

 Nereis, and cause them to stick together in masses. This is 

 never seen in acids, however strong. I can best state the sen- 

 sitiveness of the spermatozoa to KOH by giving the protocol of 

 a single experiment (June 23, 1912) which followed some prelimi- 

 nary determinations. N/10 KOH in distilled water was used as 

 the standard solution. Added to sea-water this solution produces 

 a precipitate which redissolves up to about N/2500 KOH. 



In the experiment a drop of dry sperm was stirred in about 8 cc. 

 of each of the following dilutions in sea-water, and observations 

 made as noted. 



