CHARLKS B. METZ 



29 



Fertilizin and antiferlilizin interact in antigen-antibody-like fashion (108, 

 115). The interaction is most strikingly manifested by agglutination of sjjerm 

 and eggs by fertilizin and antifertilizin respectively, and these reactions are 

 characterized by a very high order of specificity, an order of specificity, in 

 fact, which compares favorably with the fertilization reaction itself (99, 115, 

 1 16). These properties suggest that fertilizin and antifertilizin play an important 

 if not essential, role in fertilization. These substances evidently aid fertilization 

 at least to the extent that their partial removal (113, 122, 123, 127) or blockage 

 with the complementary substance (113, 127) or with specific antisera (114) 

 reduces the fertilizing capacity of the gametes. These substances may function 

 in the attachment of the sperm to the egg (115). Indeed, their interaction may 

 yet be found to constitute the activation initiating reaction. However, there is 

 no substantial evidence to support such a view, but neither are there unequivo- 

 cal data to rule it out. In spite of this rather unsatisfactory state of affairs, 

 this approach to the problem appears at present likely to be the most rewarding 

 one (see refs. 72, 97, 119). 



The approach through the medium of artificial i)arthenogenesis once seemed 

 to hold great {)romise for a clear understanding of the activation initiating 

 mechanism, and a number of interesting theories have been advanced to e.x- 

 plain the action of parthenogenetic agents. However, no common factor has 

 yet been found to unify the great body of data on parthenogenesis or to relate 

 it directly to the action of the sperm in the activation reaction. 



Other avenues of attack upon the activation problem may yet be found. 

 Interesting recent leads in this direction have been provided by the demon- 

 stration of a lipoprotein splitting action of sperm (54) and the possibility of 

 relating this action to Loeb's (51) cytolysis theory of activation. Likewise, 

 the rather striking activating action of dead paramecia upon living mates (62) 

 raises the possibility of comparable action of dead sperm on eggs. Such action 

 has not been clearly demonstrated, but a step in this direction has been attained 

 by the discovery that dead sperm will agglutinate with fertilizin (57, 70). 



b) Deviations From the AU-or-None Principle, The simplified concept of 

 activation given in the introduction, attractive though it may be, probably 

 requires some modification. Under optimal conditions the egg may appear to 

 display all-or-none, trigger-like behavior at activation, but under other con- 

 ditions deviations from the normal pattern do occur. Three possible sources of 

 such deviations should be recognized, namely 7) the activation initiating 

 mechanism itself, 2) the system for propagation of the egg responses and j) 

 the final reactions w^hich produce the morphological and physiological end 

 effects of activation. A partial failure or abnormal operation of any of these 

 three mechanisms might be expected to produce recognizable and measurable 

 deviations from the optimum expression of activation. A clear distinction can 

 not always be made among these three possibilities, since in most cases only 

 the end effects of activation can be measured. Two deviations that may relate 



