Self-Fertilization Induced by Artificial Means. 165 



spermatozoa then proceed to bore into the jelly; most of them 

 in a radial direction, although a few can be seen to go in obliquely, 

 or tangentially. The same phenomenon occurs in unripe eggs, 

 and in eggs that have been killed in weak osmic acid and the 

 acid washed out. It is improbable, therefore, that chemotaxis 

 has anything to do with the result. 



In order to see if any substance is given off by the eggs that 

 attracts the spermatozoon, the eggs were taken from the ovary, 

 carefully washed, and allowed to stand for 2 to 12 hours in a 

 small amount of sea-water. Capillary tubes were then filled with 

 this water and placed in a drop containing spermatozoa. The 

 spermatozoa did not show any tendency to collect around the 

 openings of the tubes. Several other substances were tried in 

 the tubes in the same way, — salts, sugar, ferments, acids, alcohol, 

 etc. — but no chemotaxis was discovered. 



The spermatozoa of the sea-urchins swim in spirals. Coming 

 into contact with a surface, the spiral is changed to a circular 

 movement due to contact. Buller considers whether the radial 

 path taken by most of the spermatozoa after they have entered 

 the jelly is due to stereotropism. He reaches the conclusion that 

 while theoretically this assumption will explain the phenomenon, 

 yet conclusive evidence in favour of this view is lacking. He 

 suggests that it may be possible to find a purely physical solution 

 of the problem. 



Von Dungern has examined the question of cross-fertilization 

 from the point of view of the different substances contained in the 

 egg, and has reached some conclusions of the greatest interest. 

 He finds that the egg of the starfish, Jsterias glacialis, contains a 

 substance that acts as a poison on the sperm of the sea-urchin 

 (Echinus or Sphaerechinus) . The minimal lethal dose for the 

 sperm mixed with 2 ccm of sea-water varies considerably with the 

 individual; for Echinus between 1/800 to 1/6400 part is fatal 

 in half an hour. Von Dungern tried to obtain an antitoxin from 

 the blood of the rabbit that would neutralize the effect of the 

 poison of the eggs, hoping that it might be possible in this way 

 to bring about the cross-fertilization of the egg of the starfish 

 by the spermatozoon of the sea-urchin. He found, however, that 



