STUDIES OF FERTILIZATION 525 



5. Chemical composition of the medium 



The effect of the chemical composition of the medium upon the 

 activity of the spermatozoa is a very comphcated subject, and no 

 attempt has been made to analyze it farther than was necessary 

 for comprehension of the forms of behavior studied. Even the 

 simplest experiments furnish convincing proof of the dependence 

 of activit}^ of the spermatozoa upon a constant chemical com- 

 position of the medimn; and this extreme susceptibility is 

 certainly a prime factor in the behavior of the spermatozoa. To 

 determine something of its limits becomes therefore necessary. 



One of the first questions that presents itself is obviously the 

 relation of the activity to the various salts of the sea-water. This 

 is, however, in itself a problem of so much complexity that I have 

 hesitated to undertake it; especially as it is unnecessary for our 

 present purpose, seeing that the behavior to be studied takes 

 place in sea-water as its medium. The few observations made 

 demonstrate that spermatozoa of Nereis are paralyzed in pure 

 M/2 solutions of NaCl, KCl, CaCU and MgClo. As these are 

 the principal salts of sea-water, it is obvious that the activation of 

 the spermatozoa in the sea-water is a question of balance of 

 'salts. I therefore tried Van't Hoff's solution, namely: 100 cc. 

 M/2 NaCl + 2.2 cc. M/2 KCl + 2 cc. M/2 CaCls + 12 cc. M/2 

 MgCl2, but the spermatozoa did not activate in this solution either. 

 Some other experiments were made, which did not materially 

 help the problem, which was not followed farther. The later 

 experiments all assume the sea-water as the given medium. 



Some early observations in the course of this work had shown 

 that the female excretes certain substances in the sea-water that 

 have a strong inhibiting effect upon the activity of the spermato- 

 zoa. This is so marked that sperm suspensions made up in sea- 

 water sufficiently charged with secretions of the females never 

 exhibit the aggregation phenomenon, and their fertilizing power 

 is markedly reduced. This fact repeatedly observed suggested 

 tests on the susceptibility of the spermatozoa to CO 2 dissolved in 

 the sea-water, and this formed the beginning of a series of tests 

 that involved acids and alkalis and some other substances. 



