MASS PHYSIOLOGY OF SPERMATOZOA 277 



Here we have a suggested sixth explanation of the greater longevity 

 of the more concentrated sperm suspensions. Some of the further 

 evidence at hand concerning the electrical nature of this relation- 

 ship, taken from the summary by Drzewina and Bohn (1928) of 

 their work, will be given. 



Sperm of sea urchins lose fertilizing power rapidly if a medium 

 concentration be placed in a silver dish. The greater the concentra- 

 tion the longer they retain this power. Diluted 100 times they 

 fertilize eggs up to an hour's exposure; diluted 10,000 times, up to 

 20 minutes; while at a dilution of 100,000, fertilizing power is lost 

 immediately. The effect is in part a function of the mass of the 

 silver acting: a thin silver foil is completely inactivated after three 

 consecutive exposures. It is reactivated if placed over a block of 

 silver but not if placed over glass. The effect on sperm is paralleled 

 by the action on the flatworm Convoluta. 



Further, hydroquinone is active when very dilute, and there is 

 good reason for belief that its activity is, at least in part, electrical 

 in nature. If so, the effect upon suspensions of sperm should be 

 illuminating. It is found that if sperm are diluted 100 times and 

 exposed to hydroquinone diluted 1,000,000 times, and then given a 

 chance within 30 seconds to fertilize normal eggs, normal fertiliza- 

 tion membranes are formed. This is not the case when sperm sus- 

 pensions diluted 1,000 times are given the same treatment; and if 

 the hydroquinone, rather than the sperm suspension, is made more 

 dilute, it also loses its effect. 



Convoluta placed in a dish lined with stearin survive only half 

 an hour, although if placed in a similar dish lined with paraffin 

 they live normally and even longer than in a glass dish. The par- 

 affin appears to exert a protective effect for the Convoluta, while the 

 stearin has a destructive action. When exposed to silver in a glass 

 dish, all Convoluta die, while those exposed similarly in a paraffined 

 dish are still alive. A paraffined dish favors survival of sea-urchin 

 eggs but is harmful to sperm. Stearin, on the other hand, is harm- 

 ful to eggs. 



Both paraffin and stearin are more chemically inert than glass 

 and are less soluble in water; yet it is sufficient merely to line the 



