88 Specificity in Fertilization 



membrane formation does not create such a block al- 

 though it puts an end to the "fertilizin" reaction. In 

 the egg of purpuratus the "fertilizin" reaction ceases 

 when the jelly surrounding the egg is dissolved by an 

 acid and the eggs are repeatedly washed; yet such eggs 

 can easily be fertilized by sperm. 



Lillie does not assume that the "fertilizin" causes 

 an agglutination between egg and spermatozoon we 

 should assent to such an assumption but that the 

 "fertilizin" acts like an "amboceptor" between egg 

 and spermatozoon, the latter being the complement, 

 the former the antigen. The pathologist would prob- 

 ably object to this interpretation since no "ambocep- 

 tor" is needed for agglutination. The writer has had 

 some doubts concerning the value of Ehrlich's side- 

 chain theory which, besides, can only be applied in a 

 metaphorical sense to the mechanism of the entrance 

 of the spermatozoon into the egg. 1 



1 Loeb, J., Am. Naturalist, 1915, xlix., 257. 



The writer may be permitted to illustrate by a special case his reason 

 for declining to accept Ehrlich's side-chain theory. Ehrlich and Sachs 

 found that if to a given mass of toxin small quantities of antitoxin are 

 added successively the first fraction added neutralized more than the 

 later fractions; and on the basis of this reasoning Ehrlich concluded 

 that ten different toxins were contained in the diphtheria toxin. Ar- 

 rhenius showed that the same phenomenon can be obtained when a 

 weak base like NH 4 OH is neutralized by a weak acid (e. g., boric 

 acid) ; hence we should assume that NH 4 OH consists of ten different 

 forms of ammonia. Both cases, the saturation of toxin with anti- 

 toxin and ammonia with boric acid are equilibrium phenomena. 

 (Arrhenius, S. f Quantitative Laws in Biological Chemistry, London, 



