1 6 FRANK R. LILLIE. 



in all respects to agglutination in Arbacia previously described. 

 Such egg-waters vary in strength according to the condition of 

 the eggs used and the relative amounts of eggs to the sea-water. 

 With perfectly fresh eggs added to about three times their own 

 bulk of sea-water, the egg-water of either species may attain a 

 strength of 640 agglutinating units, i.e., such an egg-water may 

 be diluted 640 times and still cause a minimum agglutination re- 

 action in sperm suspensions of its own species. 



The egg-waters of S. purpuratus are more variable in strength 

 than those of 5\ franciscanus due to the fact that the jelly layer, 

 which contains the larger part of the detectable agglutinating 

 substance, is relatively very soft in purpuratus eggs and is rapidly 

 lost by washing the eggs. Thus washed eggs of purpuratus 

 rarely give as high an egg-water test as washed eggs of 

 franciscanus. 1 



The agglutinating reaction is so prompt and unmistakable that 

 it was really a great surprise to find that egg-waters of maximum 

 strength may be entirely devoid of agglutinating action on the 

 sperm of the other species, even undiluted. 



The egg water of S. franciscanus never has the slightest ag- 

 glutinating action on the sperm of 5\ purpuratus. The absence 

 of reaction in this case was so invariable that it seems unneces- 

 sary to cite instances. 



On the other hand, the egg-water of the majority of individuals 

 of purpuratus may cause an apparent agglutination of the 

 sperm of franciscanus; so that we may have the appearance of a 

 lack of agreement between the reciprocals in this case just as we 

 found between Arbacia and Nereis, and between Arbacia and 

 Echinarachnius (Just). The egg-water from certain purpuratus 



i 1 have confirmed Loeb's observation that eggs of purpuratus from which 

 the jelly has been removed by acid do not produce sufficient agglutinating sub- 

 stance to agglutinate the spermatozoa. Such eggs are nevertheless capable of 

 fertilization as Loeb has stated. The eggs of franciscanus, however, after 

 removal of the jelly by acid continue to produce amounts of agglutinating 

 substance sufficient to agglutinate its own spermatozoa. In this respect fran- 

 ciscanus agrees with Arbacia (Lillie, 1915). I should regard the result in the 

 case of purpuratus as showing that an amount of fertilizin insufficient for 

 sperm agglutination is yet adequate for fertilization; and would reject Loeb's 

 ready interpretation that the fertilizin is not necessary for fertilization. 



