MASS PHYSIOLOGY OF SPERMATOZOA 271 



Figure 28, from Lillie, shows a photograph of aggregations of 

 sperm of Nereis in sea-water. His account of the formation of these 

 aggregations is as follows: 



"If a drop of dry sperm from a mature Nereis is mixed in about 

 6 cc. of sea water in a Syracuse watch crystal it makes a uniformly 

 milky suspension; in a few seconds clouds begin to appear, and in 



Fig. 28. — A sperm suspension of Nereis taken 90 seconds after mixing the sus- 

 pension. (Drawing by Toda from photograph pubHshed by Lillie, 1919. 



1 5 to 45 seconds these usually draw together into white soHd masses 

 uniformly spaced through the fluid. The intervening fluid becomes 

 quite clear and the masses quickly settle on the bottom. The rate 

 of formation of these masses and their iiumber and size depend on 

 the condition of the animal furnishing the sperm, temperature, 

 'freshness' of the sperm, reaction of the medium, etc. Sperm sus- 

 pensions of most animals do not, however, exhibit such marked 

 aggregations." 



Lillie believes, as a result of well-planned experiments, that these 



