STUDIES OF FERTILIZATION 559 



active sperm suspension was divided in two parts, and one part was 

 agglutinated by the addition of about 40 per cent of its own volume of 

 the egg-extract described above, to the other an equal amount of sea- 

 water was added. The first was strongly agglutinated; after reversal 

 both suspensions were stirred up, and beginning thirteen minutes after 

 agglutination a series of fertilizations were carried out by adding one 

 drop of the agglutinated sperm suspension to a measured quantity of 

 eggs in about 9 cc. of sea-water at 10 minute intervals. Each fertiliza- 

 tion had a control of the same quantity of eggs fertilized with one drop 

 of the control sperm. The consistent result was that about 16 per cent 

 of the eggs fertilized with the agglutinated sperm segmented and at 

 least 33 per cent of the control. The non-agglutinated spermatozoa are 

 about twice as effective as the agglutinated. But a considerable degree 

 of recovery of some spermatozoa of the agglutinated suspension is 

 shown. 



2. Nereis. Experiments with Nereis did not give such a marked 

 reduction of the fertilizing power of agglutinated sperm as in Arbacia. 

 There was, however, a marked delay in the formation of jelly when agglu- 

 tinated sperm was used as compared with normal sperm. 



It is somewhat difficult to make a satisfactory interpretation 

 of the effect of agglutination on fertilizing power. On the one 

 hand we may suppose that a certain proportion of spermatozoa 

 resist the agglutination effect, and are alone concerned in any 

 fertilizing power of an agglutinated suspension; on the other hand 

 it might be supposed that the agglutinating effect does not modify 

 fertilizing power except as it decreases the motility of the sperma- 

 tozoa or that the effect is reversible under the condition of the 

 experiments. Either assumption would be consistent with the 

 facts. 



8. CONDITIONS OF FORMATION OF THE AGGLUTININ BY THE EGGS 



The conditions of excretion of the agglutinating substance by 

 the eggs into the sea-water is quite different in the two forms. 

 In Arbacia the agglutinin is excreted continuously by unfertilized 

 eggs in such amounts that I have not succeeded even by repeated 

 washings in removing it all. Fertilization does not appear to 

 increase or decrease the quantity. In Nereis, on the other hand, 

 unfertilized eggs secrete but little of it, and one or two washings in 

 sea-water will completely remove it so that the eggs secrete no 

 more in detectable quantities; but at the moment of fertilization, 

 on the other hand, it is poured forth in advance of the jell}' in 



