PHYSIOLOGY OF THE SPERMATOZOON 115 



neither author gives any quantitative data it is dif- 

 ficult to find the cause for the disagreement. As I 

 have pointed out before, the tube method is crude as 

 compared to the injected-drop method, being ten to 

 twenty times less delicate. A negative result cannot 

 be trusted for this reason, and a positive result is not 

 necessarily due to chemotactic orientation, for sper- 

 matozoa once in such a tube, even by chance, might be 

 imprisoned there by any paralyzing effect of the 

 contents. 



The agglutination effect is a very definite and char- 

 acteristic reaction, differing from mere aggregation in 

 the following particulars: in the latter the spermatozoa 

 are merely loosely associated, and slight agitation is 

 sufficient to scatter them; in the agglutinated masses 

 the spermatozoa are stuck together and are not sepa- 

 rated by shaking. In the case of Nereis, where the 

 agglutination is firmer than in Arbacia, the masses may 

 be broken up into smaller coherent masses by needles 

 or preserved intact in killing fluids. The agglutinating 

 substance also produces its characteristic effect when 

 shaken up and evenly distributed in a vial of sperm 

 suspension, but an aggregative substance cannot of 

 course exert a chemotactic effect in the absence of a 

 gradient. The agglutination reaction is also spontane- 

 ously reversible, unlike aggregation; moreover, it can- 

 not be repeated if the reaction is complete, owing to 

 complete fixation of the agglutinable substance born by 

 the spermatozoon. Although at one time Loeb (1914) 

 held that the agglutination was probably a "tropistic 

 phenomenon," he has since abandoned this view (1915, 

 p. 275). The agglutinated spermatozoa are living and 



