An Introduction to a Biology 



opposite of what one would expect. Expect from what '^ 

 From one's — possibly unconscious — belief in the Law of 

 Diminishing Individual Contribution. 



Another case. Now that we know that a blue Anda- 

 lusian fowl is a heterozygous form produced by mating a 

 black and a white, and that Andalusians when mated 

 together produce 25% Blacks, 50% Andalusians, and 25% 

 Whites, we no longer try to get a pure strain of Andalu- 

 sians by throwing away the blacks and whites and by con- 

 tinuing to breed from the Andalusians for many genera- 

 tions, because we know that we can always get Andalu- 

 sians and nothing else by mating blacks and whites. ^ What 

 is the conception of heredity which underlay the old-fashioned 

 attempt to breed pure Andalusians by weeding out the 

 blacks and whites, but the Law of Diminishing Individual 

 Contribution ? 



Again, Coutagne,^ in discussing the possibility of the 

 hybrid nature of some dark-lipped individuals of Helix 

 hortensiSy which occurred in a collection of that species and 

 Helix netnoralis living in one locality, concluded from the 

 fact that these supposed hybrids were unhanded, whereas 

 the great majority of the H. nemorcdis in that locaHty were 

 banded, that they were not hybrids. To translate his own 

 words, "If the H. neinoralis were the parents of the 113 

 black-lipped individuals there is every reason to beheve 

 (tout porte d presumer) that this character of banding would 

 appear at least in some cases in these 113 individuals." 

 Through Lang's ^ work we know now that in a cross between 

 a banded H. nemoralis and an unhanded H. hortensis the 

 unbandedness is dominant. So that now we should twt 

 expect " this character of banding " to appear in any of 

 the individuals : and Coutagne's argument falls to the 

 ground. 



But what is " tout forte a presumer " but the expectation 



1 Punnett, :05, p. 28. ^ Coulagne, :95, p. 72. 



^ Lang, :04, p. 497, and :0G {see aho Daibishire, :U56, p. 190). 



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