STl'DIKS IN 'I Hi'. PHYSIOLOGY < >K SI'KK MAH )/( )A. 



jectecl to different en vironments was determined by adding such 

 sperm in identical concentration to the ripe eggs of the same 

 species in sea water at different times. The average number of 

 eggs that subsequently developed was estimated by counting at 

 least a hundred eggs at about the four cell stage. 1 



In tabulating the experiments that are reported (in Tables 

 I., II. and III. the concentration of spermatozoa was the variable 

 environmental condition) the concentration of spermatozoa in 

 the suspension is recorded in a column at the extreme left. The 

 variable environmental conditions that obtained in the different 

 suspensions are recorded in a legend over the columns repre- 

 senting the percentage of eggs that w r ere fertilized when a definite 

 number of drops of the sperm suspension (the number of drops of 

 sperm is reported either in the legend or in a column at the ex- 

 treme right) were added to a constant quantity of eggs in a given 

 amount of sea water at the intervals noted. 



The effects of change in environmental condition upon sperm 

 were under investigation. Since the influence of change in 

 environmental condition upon eggs and upon sperm are not 

 dissimilar (Loeb, J., 1913, Robertson, T. B., 1912) the variation 

 in the physiological condition of eggs (Gemmill, 1900; Vernon, 

 1899; Loeb, J., 1913; Goldfarb, A. J., 1917) was eliminated by 

 always inseminating in sea water. 



For the same reason, the eggs of but one female were used in 

 each series of inseminations. The fertilizing power of different 

 sperm suspensions were in this w r ay tested. The eggs were ob- 

 tained by straining the cut up ovaries through cheese cloth into 

 sea water, and subsequently washing the eggs by decanting the 

 supernatant fluid. Eggs were never used after they had been 

 in sea water for more than six hours. The forceps that were 

 employed in removing the ovaries were never used for any other 

 purpose. If a male had previously been opened, the hands and 

 the scissors with which the peristome had been cut were rinsed 

 in fresh water. A control of unfertilized eggs was always kept, 

 but no contamination was ever observed. 



The failure of sperm to fertilize ripe eggs may be employed as 



1 See Lillie, F. R., 1015; Fuclis, II. M., 1915, for a detailed description of this 

 procedure 



