SPERM FILTRATES AND DIALYZATES. 333 



Experiments to determine whether the substance or substances 

 present in filtrates and dialyzates are "tissue specific," acting 

 only on ova, have not been undertaken. It is true that they do 

 not cytolyze species sperm, as the latter retain their fertilizing 

 power after prolonged exposure to such preparations. The latter 

 are not "species specific" since they readily activate ova of 

 unrelated species. Tests have not been performed to determine 

 whether the effect on species and on foreign ova is due to the 

 same constituent of the preparations. 



If the substance acts as a superficial cytolytic agent as sug- 

 gested by Loeb (1916), it is to be expected that membrane 

 elevation or swelling will occur in ova of the same species exposed 

 to the sperm filtrates and dialyzates. Such occurred in Nereis 

 only. However, such preparations cause partial activation and 

 changes in the protoplasm of sea-urchin ova; and there is 

 evidence that the properties of the egg surface are affected. 

 Thus, after exposure to sperm filtrates, unfertilized ova of sea- 

 urchins are more susceptible to the action of hypertonic sea- 

 water; are in a condition which facilitates polyspermy; and 

 their permeability is increased. Fertilized eggs, transferred to 

 such preparations within ten minutes after insemination in sea- 

 water, fail to develop normally. This may be due in part at 

 least to an increase in the permeability of the egg surface. The 

 sperm are uninjured by long exposure and the changes in the 

 ova are reversible if the duration of exposure to such preparations 

 is brief. 



According to the "fertilizin" theory of Lillie (1914), substances 

 ("receptors") given off by sperm activate "fertilizin " an essential 

 constituent of the. cortex of mature eggs. This in turn initiates 

 the development of the egg. If "receptors" exist in active 

 form and in sufficient quantity in these sperm filtrates and 

 dialyzates, the latter should produce the following effects: 

 initiation of development of mature ova of the same species; 

 such activation of "fertilizin" in egg- water as to make the latter 

 an efficient parthenogenetic agent; such combination with an 

 agglutinating substance in egg-water as to destroy the power of 

 the latter to agglutinate fresh sperm suspensions. The first of 

 these results only has been obtained in this investigation. If 



