526 



FRANK R. LILLIE 



a. Susceptibility to acids, including CO2. The susceptibility of 

 spermatozoa of Nereis to acids was tested by opening a male 

 Nereis in a dry watch crystal, and mixing a drop of the thick 

 sperm, which flows out, in 6 to 8 cc. of the solution, to be tested. 

 The effect on the movements of the spermatozoa was then ob- 

 served as rapidly as possible, first with the naked eye to control 

 the aggregation reaction which is given only by very active sper- 

 matozoa, and second with the microscope to note the degree of 

 activity if their movements were sufficiently slowed down to 

 prevent the aggregation reaction. For each experiment a control 

 suspension of spermatozoa in normal sea-water was run, and only 

 those experiments are taken into account in which the control 

 aggregated in ninety seconds or less. The acid solutions were 

 made by adding a sufficient quantity of N/10 dilutions in dis- 

 "tiried water to a measured quantity of sea-water to reach the dilu- 

 tions tested. These were always so weak as not to involve the 

 question of osmotic changes in the results. The results may be 

 tabulated as follows: 



H2SO4 



HCl 



HNO3 



CH3.C00H 



N/1000. . 

 N/2000.. 



N/3000. . 

 N/5000.. 

 N/10000. 







1- 



2+ 



4 



4 



In this table (0) stands for complete paralj'sis 



(1) represents minimum amount of movement; usually only a few 



spermatozoa moving 



(2) Fairly active, but no aggregations form 



(3) Active; aggregations form, but are few in number and require 



over two minutes to appear 



(4) represents maximum activity, aggregations forming at least as 



rapidly as in the control, i.e., in less than ninety seconds 



While the four grades of activity noted are readily to be dis- 

 tinguished in Nereis, their relation to the grades of acidity in ques- 

 tion is not to be taken as fixed and invariable. As a matter of 

 fact the various observations show considerable variation with 

 reference to the intermediate dilutions, N/2000 to N/5000, in the 

 case of the mineral acids. But in the case of the extremes N/1000 



