SEVENTH ANNUAL MEETING 33 



The substance is more of less specific in as much as it will not 

 agglutinate the spermatozoa of Nereis for instance. Professor 

 Loeb has since been able to determine a higher degree of spec- 

 ificity, as between related species of sea-urchins 



It is possible to study the production of this substance quan- 

 titatively, that is to say, a given bulk of ripe eggs may be 

 shown to charge a given amount of sea-water to an extent that 

 may be measured in the following way : The agglutination as 



noted, is reversible. It is therefore possible to establish a 

 minimum reaction as unit in which reversal takes place in four 

 to five seconds. Then the amount of dilution of a given agglut- 

 inating solution necessary to reduce it to unit strength is a 

 measure of concentration of the agglutinating substance. 



To give an idea of the quantities involved it may be stated 

 that sea-water which has stood over one quarter its bulk of ripe 

 eggs for half an hour may be capable of 1/800 to 1/3200 dilu- 

 tion, or is of the strength of 800 to 3200 agglutinating units. 

 By another method we may ascertain that a single c.c. of the 

 eggs placed in 8000 c.c. of sea-water will charge the whole body 

 of sea-water w r ith sufficient quantity of the agglutinating sub- 

 stance to be detected. The unfertilized ripe eggs of Arbacia 

 produce this substance as long as they live and remain in a 

 fertilizable condition; they may be washed repeatedly in sea- 

 water, and when restored to fresh sea-water this is soon found 

 to be charged with the substance in question. In certain ex- 

 periments I have carried out thirty-five successive washings of 

 a given lot of eggs during a period of three days without being 

 able entirely to dispose of the agglutinating substance. 



Definite quantitive relations in the reaction with the sperm 

 suspension may also be estimated by the number of units of the 

 agglutinating substance which can be neutralized by a given 

 standard suspension of the spermatozoa. For the details, I 

 must refer to previous papers. 



On account of the activity of the eggs in producing this sub- 

 stance and the avidity of the sperm for it, it seems reasonable 

 to assume that it plays some part in the normal fertilization 

 reaction. 



It was therefore interesting to find that the eggs contain a 

 substance, which they do not normally secrete, which neu- 

 tralizes the sperm-agglutinating action of the egg-secretion, 



♦These observations must be made under the microscope: a quantity 

 of sperm suspension is mounted on a slide under a raised cover slip, 

 and a drop of the fluid to be tested is injected into the suspension by 

 means of a capillary pipette. 



