114 PROBLEMS OF FERTILIZATION 



intact.^ In this case the ring of spermatozoa remains 

 unagglutinated. Thus the aggregating and agglutinating 

 substances are distinct. We have previously discussed 

 the significance of the ring formation with external 

 clear zone with reference to acids in the case of Nereis 

 and arrived at the conclusion that this is a true chemo- 

 tactic reaction of spermatozoa; the same conclusion 

 must hold for the egg water of Arbacia, which thus 

 contains a substance derived from the eggs which 

 determines aggregation of spermatozoa. 



Egg substances that thus activate and direct the 

 specific spermatozoa and render them adhesive are well 

 adapted to favor the fertilization reaction which we 

 shall consider later. 



Doubt has been expressed as to the presence of a 

 chemotactic agent in egg secretions of animals. Buller 

 (1902), who investigated the subject in various species 

 of sea urchins, using the tube method of Pfeffer, ob- 

 tained only negative results. He states that they went 

 in and out of the tubes containing egg water with indif- 

 ference, and he failed to discover any other substance 

 to which they would give a chemotactic response in 

 the sense of entering the solution in the tubes and 

 remaining there. J. de Meyer (191 1), later using pre- 

 cisely the same methods, often obtained plugs of sper- 

 matozoa several millimeters long in tubes containing egg 

 water. He thus disagrees entirely with Buller; but as 



^ While this book was in press there appeared Forced Movements, 

 Tropisms and Animal Conduct by Jacques Loeb, in which he again 

 returns to the attack against chemotropism of spermatozoa. His some- 

 what inaccurate account of the writer's views and experiments lends 

 some plausibility to criticisms which have no real foundation; the funda- 

 mental problem involved receives no real consideration. 



