stout: pollinations in cichorium intybus 431 



interaction. In Correns' results cross-sterility is considered^ as a 

 result of interaction of inhibiting substances and cross-fertility is 

 an index that there was no action. These interactions expressed 

 by + and - are represented in table 17. A comparison of the 

 behavior of cross-sterility between the various classes of Cardamine 

 and the agglutination reactions between the various groups of 

 man and steers shows that the only agreement is seen in the ab- 

 sence of reactions exhibited by class " a6 " in Cardamine, the class III 

 in steers, and class I in man. Only in classes in which all reacting 

 substances are assumed to be either latent or absent is there any 



agreement. 



There is as yet no evidence that these phenomena of isoaggluti- 

 nation have any relation to the cross-fertility of the animals con- 

 cerned, for fertility between the individuals showing agglutination 

 is apparently unimpaired. Thus it is evident that differentiations 

 do occur, giving so-called incompatibility between blood cells and 

 sera of animals of the same species which, as far as known, have 

 no influence on the compatibility of the sex cells themselves. 

 These observations suggest strongly that analogous reactions may 

 operate in the cytoplasmic relations involved in the growth of 

 pollen tubes during the early processes of fertilization, and that 

 such interactions are not necessarily an index of the direct relations 

 of the sex cells. 



Physicians, however, fully recognize that cases of human 

 sterility may involve particular incompatibilities which may be of 

 the nature of those shown in immunity reactions either natural or 

 acquired. The exact nature of these incompatibilities are, of 

 course, at present no more understood than are the cases in plants 

 (see discussion by J. B. De Lee of article by Edward Reynolds, 

 '15), but De Lee believes that they may prove to be related to ag- 

 glutination reactions. 



That sterility may be a type of immunity and that the coni- 

 patibility of the gametes themselves will depend on their consti- 

 tutional similarity rather than their so-called sex differentiation is, 

 however, very strongly indicated by the general evidence from 

 agglutination reactions. 



The observations made by Lillie ('12-'16) give strong support 

 to the doctrine, rather generally discredited among zoologists, of a 

 specific chemotactic influence of egg secretions on sperms. His 



