lO Darbishire, Laivs of Heredity. 



together produce 25 per cent. Blacks, 50 per cent. Anda- 

 lusians, and 25 per cent. Whites, we no longer try to 

 get a pure strain of Andalusians by throwing away the 

 blacks and whites and by continuing to breed from the 

 Andalusians for many generations, because we know that 

 we can always get Andalusians 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 Coutagnef, in discussing the possibility of 

 the hybrid nature of some dark-lipped individuals of 

 Helix hortensis, which occurred in a collection of that 

 species and Helix nevioralis living in one locality, 

 concluded from the fact that these supposed hybrids were 

 unhanded, whereas the great majority of the H. nemoralis 

 in that locality were banded, that they were not hybrids. 

 To translate his own words "If the H. nemoralis were the 

 parents of the 113 black-lipped individuals there is every 

 reason to believe {tout porte a pr^sunier) that this char- 

 acter 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 not expect " this 

 character of banding " to appear in any of the indi- 

 viduals : and Coutagne's argument falls to the ground. 



But what is '' tout porte a pnfsuiner" but the expecta- 

 tion based on a firm belief in the Law of Diminishing 

 Individual Contribution? 



* Punnett, 105, p. 28. 

 t Coutagnc, :95, p. 72. 

 + Lang :04 (p. 497) and :06. See also Darbishire .O^f', p. 196. 



