SPERM FILTRATES AND DIALYZATES. 3OJ 



according to the method of Gates (1921). The sacs were washed 

 in redistilled water and in sea-water. Samples of sea-water, 

 allowed to stand in the washed sacs for at least twelve hours, 

 were tested in the same manner as that passed through the 

 diatomaceous filters. Tests for leakage were made and any im- 

 perfect sacs were discarded. Ten milliliters of twenty-five or of 

 fifty per cent, suspensions of sperm were placed in a tested 

 collodion sac and dialyzed against forty milliliters of sea-water. 

 The resultant dialyzates may be considered comparable to filtrates 

 prepared from five and ten per cent, suspensions of sperm. The 

 sea-water dialyzates must be aerated constantly to provide the 

 most favorable conditions for the sperm during the process. This 

 involves two dangers: evaporation and contamination of the 

 dialyzates. In order to eliminate these sources of error the 

 method illustrated in Fig. i was employed. 



In these experiments dialysis was continued for five to twenty- 

 four hours. With one exception the sperm in the collodion sacs 

 retained their fertilizing power and their capacity for iso-aggluti- 

 nation at the end of the process. 



III. PROPERTIES OF PREPARATIONS. 



a. Physical and Chemical Properties. The osmotic pressure of 

 filtrates and dialyzates, as indicated by the specific gravity tests, 

 is the same as that of sea-water. There is a slight variation in 

 some preparations and in sea-water but it is not sufficient in 

 itself, as determined by experimentation, to produce activation. 

 The hydrogen-ion concentration of filtrates and dialyzates was 

 also equal to that of sea-water (p H 7.9-8.1 at Woods Hole; 

 7.6-7.8 at Pacific Grove), indicating that the carbon dioxide 

 formed by active sperm was completely removed by aeration 

 and that the sperm added no other free hydrogen-ions. There 

 is a possibility that small amounts of acid may have combined 

 with buffers in sea-water. The question now arises whether these 

 preparations contain any active physiological principle. No 

 living spermatozoa or fragments were ever observed, nor was 

 there ever a case of normal fertilization in any of the preparations. 

 It is also certain that they contain no chemical substance whose 

 concentration falls within the range of sensitivity of the usual 

 chemical methods. 



