STRUCTURAL CHANGES AT FERTILIZATION 97 



tion, in the way that the action potential might be said to be the 

 important feature in nervous reactivity; or are calcium release, 

 cortical liquefaction and cytoplasmic gelation just some of the 

 many manifestations of the differences between fertilized and un- 

 fertilized eggs, which will only be seen in correct perspective many 

 years hence ? In any case, is it legitimate or logical to talk about the 

 important feature in any biological reaction ? Is the action potential 

 more important than the liberation of acetyl choline at a nerve 

 junction? Such questions are meaningless. The most we can do, 

 and all we need to do, in describing some biological phenomenon, 

 is (ultimately) to make a time-sequential analysis of the pheno- 

 menon in the language of physical chemistry. If calcium release 

 comes first in the fertilization reaction, we can, if we wish, define 

 coming first in terms of prime importance. 



The idea that gelation is one of the characteristics of the early 

 phases of fertilization is supported by the work of Immers (1949) 

 on the inhibitory action of fertilizin on the coagulation of fibrinogen 

 by thrombin. This, together with the observation that periodate 

 counteracts the anticoagulating action of fertilizin and heparin 

 and, in some circumstances, facilitates fertilization (Runnstrom & 

 Kriszat, 1950), has from time to time led to the expression of the 

 view that fertilizin inhibits fertilization and that the spermatozoon 

 introduces into the egg, or releases in the egg, a factor which over- 

 comes the inhibition imposed by fertilizin. This sort of argument 

 does not bear much examination. In so far as an unfertilized egg 

 is not a fertilized one and that morphological observations for more 

 than a hundred years have shown that fertilization unleashes all 

 sorts of anabolic reactions which are obviously catalyzed by 

 enzymes, the mere statement that the unfertilized egg is in an in- 

 hibited condition and that enzyme systems are activated at fer- 

 tilization is only a re-statement of the morphological facts. What 

 we must do is to identify the activated enzyme systems and the 

 chemical nature of the so-called inhibition. As regards the former, 

 a little progress has been made ; in the case of the latter, the idea 

 that fertilizin is responsible is a little difficult to swallow. 



Apart from being concerned in cortical liquefaction and cyto- 

 plasmic gelation, calcium is important in other ways in fertiliza- 

 tion and in the physiology of the gametes. In marine invertebrates, 

 it must be present in the external medium for fertilization or, for 

 that matter, the fertilizin-antifertilizin reaction, to take place at 



