Self -Fertilization Induced by Artificial Means. 175 



of some sort that directly effects the entrance of the spermatozoon 

 into the egg, and at present I see no other interpretation that is 

 left than that this entrance is due to the greater activity of the 

 spermatozoon that causes it to overcome some resistance, either 

 on the surface of the egg itself, or in the membrane surrounding 

 it. The nature of this resistance I did not detect, and this must 

 be the next step in the analysis. One method by which this view 

 may be tested is obvious, and has already been referred to. The 

 spermatozoa made active by sea-water must be placed in an ex- 

 tract of the eggs (or body-tissues) of the same individual, and 

 then, after a time, the eggs of another individual added. On 

 the hypothesis these eggs should be less likely to become fertihzed 

 than eggs placed directly in contact with the fresh sperm. 



It has been found that certain substances secreted by the glands 

 of the reproductive organs of the male mammal arouse the sper- 

 matozoa to greater activity. It has also been found that many 

 other substances have a similar effect on spermatozoa. It would 

 be equally interesting to discover if the secretions of other parts 

 of the genital ducts of the male or of the receptacula of the fe- 

 male, when such are present, may not bring the spermatozoa 

 to rest, or keep them quiescent until some other exciting agent 

 arouses them. It seems almost certain that this must be the case 

 in those animals in which the spermatozoa of the male are stored 

 up in receptacula of the female, as for instance in the honey bee, 

 or in such a hermaphroditic animal as the earthworm. The 

 length of life of the spermatozoa in some of these forms would 

 seem to make some assumption of this sort necessary. Experi- 

 ments can easily be made that would decide this question. Kol- 

 liker has shown, in fact, that water quiets the spermatozoa of 

 mammals without killing them. 



In the ascidians it is probable that the spermatozoa in the vas 

 deferens are quiescent. It is significant that in these hermaphro- 

 ditic forms the oviduct in which the eggs are stored takes a course 

 parallel to the male duct. Possibly the proximity of the two 

 ducts may be connected with the lack of power of self-fertilization 

 of the eggs, because the egg may be saturated with the same 

 substances that keep the sperm quiescent. It may be, however, 



