474 MARIE A. HINRICHS. 



(Fuchs, '15), found that some egg secretions may produce an 

 increase in the fertilizing power of the sperm of another species. 

 Clowes and Bachman, '20, have obtained a volatile sperm- 

 stimulating substance from Arbacia eggs. 



On the other hand, a number of agents have been used to 

 inhibit the activity of sperm, for example, neutral red in the 

 presence of light, ultraviolet radiation, radium, temperature, x-- 

 rays, the electric current, and various chemicals. 1 (See Bohn 

 and Drzewina, '236, Lillie and Baskervill, '22, Oppermann, '13, 

 Dungay, '13, Bardeen, '07, Guhther, '07, Cohn, '17, Gee, '16, 

 and others for references.) KCN, which interferes with normal 

 oxidation processes, was found by Drzewina and Bohn, '12, to 

 inhibit the activity of sea urchin sperm as well as to cause 

 irregular cleavage and abnormal development of eggs fertilized 

 by the treated sperm. The ageing of sea urchin germ cells has 

 been found by Goldfarb, '17, '18, to proceed more rapidly after 

 their removal from the body. Correlatively motility and ferti- 

 lizing power are reduced. Hyperalkaline sea water accelerates 

 the ageing process. 



Time and dilution are both known to be factors affecting the 

 fertilizing power of Arbacia sperm (F. R. Lillie, '156). Drzewina 

 and Bohn, '236, also showed dilution to be a factor in the suscepti- 

 bility of sea urchin sperm to the combined action of neutral red 

 and light. Motility and fertilizing power were lost more quickly 

 in dilute than in concentrated sperm suspensions. Usually loss 

 of motility is associated with loss of fertilizing power, but the 

 two do not exactly parallel each other. Fertilizing power is not 

 a function of motility alone, and declines more rapidly than 

 does motility. (See F. R. Lillie, '156, and Lillie and Just, '24.) 

 Sperm may be injured in such a way that its fertilizing power, 

 as measured by the proportion of eggs fertilized and the normality 

 of the cleavage and development, is materially lessened while 

 motility is not visibly impaired. (See also Hinrichs, '266, and 

 Lillie and Baskervill, '22.) 



1 It has been repeatedly pointed out, especially by O., G., and P. Hertwig, 

 (see previous paper for references) that the effect of injury on the sperm is par- 

 ticularly felt by the nuclear material. Packard, '14, however, suggests also a 

 possible effect on the cytoplasm. He postulates the presence of enzymes which 

 may be injured by radiation. 



