220 NEIL S. DUNGAY. 



IV. EXPERIMENTS. 



The sexual products of both Nereis and Arbacia were utilized 

 for experimental purposes. However at the time when I could 

 use Arbacia, the control cultures did not run as well as might 

 be desired and so Nereis material was used for the greater part 

 of the work. 



A. Upon Nereis. 



In the earlier experiments upon Nereis I subjected the sperm 

 cells for a certain time to the action of graded strengths of various 

 reagents. Later I found that the most satisfactory procedure 

 is to keep the sperm cells, after removal from the body of the 

 male, until they are nearly dead or to keep them for a few minutes 

 at a temperature of about 44 C. The latter method seems to 

 be less open to criticism since no substances of a possibly toxic 

 action are transferred to the egg cultures by the process of 

 insemination. 



All of the methods of experimentation which were used give 

 essentially similar results, indicating that the action upon the 

 sperm cells is probably not specific in any case. It seems rather 

 that there is produced a general decrease in vitality which may 

 manifest itself by a retarded development, by a high mortality 

 or by the production of forms w r hich are more or less abnormal 

 in structure or behavior. 



i. Heat. Perhaps the most uniform results in the whole 

 series of experiments which I have carried out were obtained 

 through the exposure of the sperm cells to a certain degree of 

 heat. This was accomplished by mixing the sperm cells with 

 sea water, which was then placed in the bottom of a test tube, 

 care being taken to prevent any of the liquid from touching the 

 walls of the upper part of the tube. A thermometer was then 

 introduced into the bottom of the test tube and was used to stir 

 the liquid and to take the temperature readings every minute. 

 The test tube was nearly immersed in a large beaker of warm 

 water. The temperature was maintained in the bath thus 

 formed, by means of an alcohol lamp or by adding to the bath 

 warmer water from another container. In this manner it is 

 possible to keep the temperature under reasonable control. 



