232 PROBLEMS OF FERTILIZATION 



The writer (1914) used the phenomenon of inhibition 

 of fertihzation by blood of the species in an attempt 

 to approach this problem a little more closely. In 

 Arbacia the presence of a certain concentration of the 

 perivisceral fluid (blood) of certain individuals inhibits 

 fertilization completely. This is not because aggluti- 

 nation is prevented, for the sperm will agglutinate in 

 any concentration of such blood. Neither is it merely 

 a general colloid effect, such as Robertson (191 26) held 

 might inhibit fertilization, because the blood of some 

 individuals has no such action. The writer there- 

 fore reasoned that the action of the blood might be 

 directed against the activating substance of the egg; 

 if this were so, and if the activating substance were 

 contained in the secretions of the eggs like the ag- 

 glutinating substance, it should then be . possible to 

 neutralize the inhibiting action of the blood by saturat- 

 ing it with egg secretions, because the inhibiting sub- 

 stance would then be combined. As a matter of fact 

 it was found that blood which is first treated with large 

 quantities of eggs, and which therefore possesses a high 

 agglutinating power, has lost its power of inhibiting ferti- 

 lization. The inhibiting action of the blood may therefore 

 be regarded as a deviation effect, in the sense that the 

 activating substance in the presence of blood exerts its 

 effect on some constituent of the blood and not on the egg. 

 This still does not prove that sperm agglutination 

 and egg activation are due to the action of a single 

 substance, but it shows again by a different method 

 that the capacity for producing both effects is present 

 simultaneously in the egg secretion, and the assumption 

 of a single substance is the simplest hypothesis. 



