Self -Fertilization Induced by Artificial Means. 167 



tinizing jelly would fail to be fertilized. The substance in the 

 sea-urchin's egg that agglutinizes the starfish sperm can be ren- 

 dered ineffective by the rabbit's serum. Not all starfish sperma- 

 tozoa are agglutinized by the jelly or by the egg-substance of all 

 the different sea-urchins. In Sphaerechinus it fails to occur. 

 Therefore in this case the failure to cross-fertilize must be due 

 to some other factor, and, in fact. Von Dungern claims to have 

 found still another substance in the sea-urchin's egg that excites 

 to greater activity the immature and quiescent spermatozoa of 

 the starfish. These immature sperm, made active by this sub- 

 stance, are then capable of fertilizing the eggs of the starfish. 

 He found that weak doses of chloral hydrate and of cocaine also 

 make these quiescent spermatozoa active, and that rabbit's serum 

 has a marked effect. Von Dungern believes further that these ex- 

 citing substances may actually prevent, in certain cases, the cross- 

 fertilization, because they may change the kind of reaction shown 

 by the sperm. He observed that the spermatozoa of those 

 species that do not normally show rotational movements when 

 they come in contact with surfaces, usually do so when the excit- 

 ing substances just mentioned are present. It does not appear 

 to me, however, that this is an altogether satisfactory explanation 

 of the failure of cross-fertilization in these cases. 



Von Dungern also examined the question as to whether the 

 egg secretes a substance that favours fertilization by its own 

 sperm. He believes that he has also discovered such a substance. 

 The eggs of Echinus (or of Sphaerechinus) are rubbed up and 

 mixed with pieces of jelly that have been carefully washed. When 

 sperm is added to the water in which such pieces lie they stand 

 vertically to the surfaces of the pieces. If on the other hand the 

 pieces of jelly are not mixed with the substance from the egg, the 

 spermatozoa simply rotate on the surface of the jelly, and do not 

 stand vertically. Starfish spermatozoa with Arbacia jelly be- 

 have as with simple jelly alone, i. e.^ they do not stand vertically. 

 The vertical position of the spermatozoa is due. Von Dungern 

 thinks, to the presence of some substance in the extract that lowers 

 the excitability of the spermatozoon to contact, and hence it takes 

 a vertical position. He also points out that this same substance 



