ULTRAVIOLET AND ARBACIA FERTILIZATION'. 419 



'15). In these experiments, cleavage is irregular and 50 per cent, 

 of the eggs are cytolyzed following a 3 inin. exposure, and from 

 50-75 per cent, are cytolyzed by exposures of 5 min. or longer. 

 In general, where the percentage of abnormal cleavage and subse- 

 quent abnormal development is high, the fertilizin production is 

 correspondingly low. Lillie and Just, '24, p. 487, call attention 

 to the coincidence of the production of agglutinating substance by 

 mature eggs with the fertilizable period of such eggs. (Lillie in 

 1914, and Just, in 1919, determined such a relation for Arbacia 

 and Echinarachnius, respectively.) 



The production of fertilizin is also decreased as membranes 

 begin to form. A series of acid-treated eggs (with the jelly re- 

 moved by the acid) showed no appreciable difference in the 

 amount of fertilizin produced during successive intervals when 

 compared with untreated eggs. (See discussion, Lillie and Just, 

 '24, p. 492.) These tests were made to determine whether ferti- 

 lizin was retained by the jelly and then given off into the sea- 

 water in large amounts as though secreted by the jelly. The jelly 

 appears to adsorb fertilizin, as will be described later, and the 

 adsorbed fertilizin retains enough of its activity to attract and 

 agglutinate sperm to the egg surface. Lillie suggests that the 

 jelly acts as a protection against loss of fertilizin (Lillie, '19, p. 

 142). Sperm show a greater avidity for eggs radiated for short 

 intervals than for non-radiated eggs, a fact suggesting an increased 

 production of some substance which attracts them. (See also 

 Table I.) 



It will be seen that the rate of production of fertilizin in radi- 

 ated eggs decreases as the time following radiation increases, and 

 at a more rapid rate than in non-radiated eggs. The total pro- 

 duction in radiated lots is also less than in normal eggs. This is 

 probably due to an effect of ultraviolet radiation upon the egg 

 cortex, which is supposed to be the seat of fertilizin production. 



B. Radiation of Egg-water. Egg-water contains several com- 

 plex substances given off by the eggs. (See studies of Lillie and 

 Just, '24, p. 483.) When such egg-water is exposed to ultra- 

 violet radiation, its various components appear to be separately 

 affected. The echinochrome pigment is faded, and the activating 

 and agglutinating substances lose their effectiveness, all at different 



