ULTRAVIOLET AND ARBACIA FERTILIZATION. 433 



to be activated." (Lillie, '19, p. 240.) A reduction of fertilizin 

 production following a temporary slight acceleration is probably 

 due to the direct action of ultraviolet radiation upon the egg 

 cortex. R. S. Lillie and Baskervill, '22, showed that radiation 

 was effective in its direct action on the egg surface. Radiation in- 

 duces membrane formation and fertilizin production is known to 

 decrease as membranes begin to form. 



Normal active sperm show an increased avidity for eggs which 

 have been radiated a short time. Apparently this is due to the 

 fact that ultraviolet radiation increases the permeability of the egg 

 cortex, and liberates fertilizin to a greater degree than that found 

 in normal eggs. 



Normal sperm bear a substance necessary for fertilization which 

 is given off into the medium, and after a certain period of loss of 

 this substance, the fertilizing capacity of sperm decreases. Ultra- 

 violet radiation augments the normal rate of loss of this substance 

 from the sperm. (For a review of literature bearing on this sub- 

 ject, see Sampson, '26, and Hinrichs, '26c.) When radiation is 

 long enough continued, sperm lose their capacity for normal ferti- 

 lization as shown by the loss of ability of eggs, fertilized by them, 

 to produce membranes, to cleave normally, and to develop into 

 normal larvae (Hinrichs, '26^). There is a corresponding loss of 

 agglutinability of sperm by normal egg-water. Radiated sperm 

 require a higher concentration of fertilizin to produce agglutina- 

 tion than do normal sperm. The same is true for sperm which 

 have been standing for some time after removal from the gonad. 

 (See Lillie and Just, '24.) Lillie and Just also report that the 

 rapidity of onset of agglutination of sperm by means of normal 

 sea- water is a function of the motility of the sperm. Radiation 

 reduces sperm activity and also lengthens the time of onset of 

 agglutination. 



Radiation produces an increase in the viscosity of sperm sus- 

 pensions. Mond, '22, and Wels, '23, report similar findings for 

 the effects of ultraviolet and x-radiation upon proteins. In radi- 

 ated sperm, this increase in viscosity, together with a reduction in 

 motility which follows, is probably responsible for the permanence 

 of clumps which are formed as the result of radiation alone. 

 When normally agglutinated masses are radiated, the clumps be- 



