434 



J. GRAY 



abateinoiit of niovomciit owing to tho supply of available 

 energy being used up within the cells. 



Again, Loeb's comment on the significance of sperm aggrega- 

 tions is important. There is no evidence that a sperma- 

 tozoon nuist take part in an aggregation before it can effect 

 fertiliisation. Aggregation need be nothing more than an 

 interesting corollary to the activation of the sperm by the 

 egg-secretion. 



Subsequent to forming active aggregations in water contain- 

 ing egg-secretions, the sperm may adhere to each other in dense 

 masses (e. g. Nereis); in certain species no such agglutination 

 takes place. A consideration of the agglutination effect of 

 egg-secretions would involve a discussion of the whole mechan- 

 ism of cell agglutination ; such a discussion is not possible, but 

 the lucid sunnnary given by Buchanan (2) may be recommended 

 to the notice of any who feel disposed to follow Lillie's argu- 

 ment of specific agglutinations. The fundamental fact is that 

 agglutination depends primarily on the presence of free ions. 

 This can readily be demonstrated in the case of spermatozoa 

 or of eggs. The addition of a trivalent cation such as cerium 

 causes a very marked agglutination (Gray, 9), which Lillie 

 regards as comparable to the effect of heterofertilizin (i. e. the 

 fertilizin of one species on the spermatozoa of another). Again, 

 the addition of a small amount of sodium phosphate to normal 

 sea-water causes a marked agglutination of the sperm of 

 Echinus m i li a r i s . These phenomena depend upon the 

 deposition of an insoluble precipitate on the surface of the cells ; 

 in the case of cerium agglutination, insoluble cerium hydroxide 

 (probably in the colloidal form) is deposited on the cell-surface 

 and the cells adhere to each other by virtue of this common 

 matrix — just as particles of oil are agglutinated by ferric 

 hydroxide (Ellis, 6). Any substance which breaks up or 

 dissolves this matrix reverses agglutination ; thus acid dissolves 

 Ce(0H)3 forming cerous chloride, while alkali or sodium citrate 

 pectises or breaks up the film into non-coherent parts.^ 



1 It may be noted that this explanation differs from that offered in 

 a previous paper (Gray, 9). The conditions for the deposition of such 



