I06 E. E. JUST. 



The same experiment succeeds if one uses the water from dishes 

 in which uninseminated eggs have remained for a few minutes. 

 Washed eggs do not cause agglutination of Nereis sperm; water 

 charged -by normally inseminated eggs or uninseminated eggs 

 retains its power of agglutinating Nereis sperm after twelve 

 hours at least, the reaction coming on more slowly. The freshly 

 charged water acting on fresh sperm suspension gives a clear-cut 

 and beautiful reaction. 



It may seem far-fetched to argue that the fertilizing substance 

 lost by Platynereis eggs when exposed to sea-water is agglutinin 

 or fertilizin as discovered by Lillie in Nereis and Arhacia because 

 the washed egg, no longer fertilizable by its own sperm, can not 

 sufficiently charge the sea-water to agglutinate Nereis sperm. 

 Yet I believe this is the case precisely. The agglutination of 

 Nereis sperm by Platynereis egg- water is correlated with jelly 

 formation in Platynereis by Nereis sperm. In sea-water in- 

 seminations. Nereis spermatozoa are almost as effective as those 

 of Platynereis. Added to this is the difference in behavior of 

 Platynereis sperm in egg charged sea-water, in sea-water insemin- 

 ations, and in dry inseminations. 



The evidence may be scant, but it seems to me sufficient to 

 indicate that the substance lost which is necessary for fertilization 

 is identical in nature with the fertilizin of Lillie. 



B. Cross Fertilization with Nereis. 



I have mentioned (Just, '14) the fact that it is generally taken 

 for granted that reciprocal crossing of Nereis and Platynereis is 

 the rule. This led me to attempt cross fertilization. Cross 

 fertilization never produces segmentation or development though 

 it may induce the maturation process. 



Of the methods used in echinoderm hybridization — those of 

 Loeb, Tennent,^ etc. : (i) high temperature; (2) treatment with 

 fresh water; (3) treatment with alkalis; (4) allowing the eggs to 

 stand; and (5) polyspermy — all were tried except the first. 

 Since the eggs of Platynereis are normally inseminated in the 

 body cavity and therefore with little sea-water, I tried "dry 



1 Dr. Tennent in 1912 very kindly communicated to me at length his latest 

 methods in echinoderm hybridization. 



