306 



MYKA MKLISSA SAMPSON. 



During the passage of the filtrate it is necessary to prevent or 

 at least to minimize the destruction of spermatozoa by de- 

 hydration or compression. This was attempted by not allowing 

 the surface of the mantle to become exposed to air and by frequent 

 and cautious stirring of the suspension. Some of the spermatozoa 

 are not seriously injured in the process of filtration as indicated 

 by the isoagglutinable and fertilizing power of the sperm re- 

 maining on the surface of the mantle at the end of the process. 



The filtrates, which are automatically freed from any excess of 

 carbon dioxide in passing through the filter mantle, are then 

 transferred to flasks which are kept tightly plugged and placed 

 in a refrigerator. These solutions remain free from bacteria and 

 retain their peculiar physiological properties for at least a month. 



Preparation of Sperm Dialyzates. There is one objection to 

 the use of sperm filtrates. Some spermatozoa may undergo 

 destruction on the surface of the mantle. To meet this objection 

 I prepared dialyzates of sperm in order to compare their action 

 on ova with that of filtrates. 



A. 





FIG. i. Dialyzing apparatus. Air is drawn through the sea-water in the three 

 bottles by suction exerted at A. The collodion sac is suspended in the sea-water 

 in the central bottle and this sea-water dialyzate used in experiments later. The 

 outer two bottles serve as safety flasks. 



Collodion sacs used as dialyzers were made in fifty milliliter 

 centrifuge tubes from a twelve per cent, collodion prepared 



