EGG SECRETIONS OF ARBACIA AND ASTERIAS 463 



slimy with eggs. At that time, when 98 per cent to 100 per cent 

 of the eggs would develop normally, most of the observations on 

 the sperm agglutinin were made. All of them, however, were 

 repeated and confirmed in 1915, 1916, or 1917. 



As observed by Glaser, if a drop of sea-water, which had been 

 standing over mature Asterias eggs, was injected under a cover- 

 glass into a drop of sperm suspension, the sperm would gather 

 into small, irregularly angular clusters of six to eighteen and 

 remain agglutinated for a number of seconds which varied with 

 the strength of the solution. When they separated, they were 

 much more active than before. The general process of agglutina- 

 tion and activation is the same in Asterias as in Arbacia, where it 

 has been observed by many. The chief difference is in the size 

 of the clusters, which are smaller in Asterias. 



As is known, Asterias eggs are obtained with the germinal 

 vesicle still intact. Maturation changes begin almost immedi- 

 ately and are complete in forty-five to sixty minutes. Directly 

 after obtaining them, some of the eggs of a large female were put 

 into a centrifuge tube with two volumes of water and allowed 

 to stand ten minutes to obtain fertilizin in the standard way. 

 After centrifuging, the supernatant fluid was tested for its agglu- 

 tinative power. When diluted 1 : 200, Asterias sperm remained 

 agglutinated six seconds, a unit reaction. An hour after shed- 

 ding, the rest of the eggs from the same female, which had been 

 kept in a large amount of water, were washed twice with fresh 

 sea-water, and then the secretion obtained as before. This, 

 when diluted 1 : 200, caused a fresh sperm suspension to remain 

 agglutinated over four minutes. In other words, it was over 

 sixty times as strong as the other. Experiments of Lillie and 

 Just indicate that in Arbacia and Nereis, as well as in Asterias, 

 fertilizin is formed by the maturing or mature, but not by imma- 

 ture eggs. I believe that Lillie's failure (quoted by Loeb, 

 '16, p. 83) to verify the observations with Asterias secretion was 

 due to abnormal material. 



Loeb ('15) has observed activation of sperm of the echinoderms 

 at Pacific Grove by eggs of the same and related species. He also 

 noted that the sperm of Strongylocentrotus purpuratus are 



