ULTRAVIOLET AND ARBACIA FERTILIZATION. 



427 



Measurements of pH in these experiments on fertilizin were made 

 by the use of indicators. In the region of 6.8 to 8.2, from 75- 

 87.5 per cent, of the fertilizin was adsorbed. In another series, 

 at 7.5 to 7.9, the percentage of adsorption wa^ from 96-ioa 1 

 ( See Table VIII.) 



TABLE VIII. 



EFFECT OF pH ON ADSORPTION. 



Radiation of Sperm Suspensions. Earlier work with Arbacia 

 sperm has shown that a loss of motility and a reduction of ferti- 

 lizing power follow the exposure of sperm suspensions to ultra- 

 violet radiation. (Lillie and Baskervill, '22, Hinrichs, '26c.) In 

 these earlier experiments, it was also noted that radiated suspen- 

 sions of sperm had lost some of their opalescence and appeared 

 cleared in transmitted light. This was probably due to the settling 

 out of suspension of irregular aggregations of sperm ; such clump- 

 ing or agglutination results from exposure to ultraviolet radiation. 

 (Hinrichs, '26c.) In the present series of experiments with 

 sperm, it was noted that the decrease in opacity to light was pro- 

 portional to the dosage of radiation a given sperm suspension had 

 received. The results are recorded in Table IX. 



The relative opacity was measured by means of a nephelometer. 

 A i per cent, sperm suspension was used as stock, and from I to 

 20 drops thereof per 100 cc. of sea- water were exposed to radia- 

 tion at 12.5 cm. from the lamp, for periods of from 15 sec. to 15 

 min. As in previously reported experiments, the more dilute sus- 



1 More work is planned on this phase of the probleni. 



