1 68 T. H. Morgan. 



causes the spermatozoa to lose their power of movement in a 

 short time. Thus, while Von Dungern finds no evidence of a 

 substance in the egg that attracts the sperm, he believes that there 

 may be present in some eggs a substance that favours the fer- 

 tilization of the egg, by causing the spermatozoon to assume that 

 position in the jelly that is most likely to bring them to the surface 

 of the egg. 



Loew has attempted to show by an experiment, which is not, I 

 think, well suited to prove his point, that the spermatozoa of the 

 rat are attracted to, i. e., that they are positively chemotactic to, 

 the slime layer of the uterus and also to the alkaline mucosa of 

 the digestive tract, but not to the acid slime of the vagina. His 

 method of experimenting was as follows : A piece of the mucosa 

 of the uterus was put on one side of a slide and a piece of the 

 vagina on the other. A drop containing the sperm was placed in 

 the middle of a cover-slip, and this put over the pieces on the 

 slide. It was found that the sperm collected more on the side 

 near the piece of the uterus, and from this Loew infers that they 

 have been attracted to this side. In the light of the other experi- 

 ments described above it will be clear, I think, that the greater 

 accumulation of the sperm on one side by no means establishes the 

 conclusion that they have been attracted to this side. Loew tried 

 to show that filter paper saturated with alkaline substances acts che- 

 motactically on the spermatozoa, in the sense that they move to- 

 wards such substances, but, as in the preceding case, it does not nec- 

 essarily follow because spermatozoa collect around or in certain 

 substances, therefore they must have moved towards these sub- 

 stances. The recent work of Jennings on the protozoans shows that 

 their accumulations in certain areas is not due to the action of sub- 

 stances that cause the individuals to swim towards those sub- 

 stances, but on the contrary to their action being such that those 

 individuals that enter areas containing these substances are unable 

 to leave them. The result is the same as when the spermatozoa 

 touch the jelly of the egg and stick to it, although the means by 

 which the accumulations are formed in the two cases are entirely 

 different. It would be interesting to see if spermatozoa may 

 not behave towards certain solutions as do the protozoans. 



