1 62 Possibility of Selective [CH. 



To test whether the numerical output of gametes was 

 abnormal, reciprocal crosses were made between F^ plants 

 of the same breeding and recessives. In both cases the 

 normal equality between round and wrinkled seeds was 

 produced. Correns therefore concludes that some process 

 of selective mating was responsible for the aberrant F z 

 numbers (65). 



So far as I am aware, no case altogether similar to this 

 one has been observed, certainly none in which the numbers 

 available are so large. The proportions for maize seeds 

 are usually very regular in regard to the round and wrinkled 

 characters, as the records of both Correns and Lock testify. 



Pending further acquaintance with phenomena of this 

 class there is no more to be said. The possibility of dis- 

 turbance by selective attraction between particular kinds 

 of gametes must be recognized, though without much more 

 definite evidence its occurrence can scarcely be regarded 

 as demonstrated. 



In another instance of a different kind the same sug- 

 gestion was made by Cuenot. Of this case I have already 

 spoken* in describing the inheritance of yellow colour in 

 animals. Experimenting with mice he found it impossible 

 to find a yellow mouse pure to yellowness. Among mice 

 yellow behaves as a dominant, in the sense that agoutis or 

 blacks may be bred from two yellows. If the case were 

 an ordinary one, some of the yellows produced by the 

 mating of two yellows should be pure, and on breeding to 

 blacks or agoutis they would be expected to give all yellows. 

 Cuenot's experience is that this is never realized, and all 

 the yellows he has ever tested, amounting to 8 r individuals, 

 also show, in such matings, some colours other than yellow 

 (cp. Basset Hounds, p. 128). Miss Durham has made 

 similar experiments with the same result. Yellows were 

 always found to give off either agoutis, or blacks, or 

 chocolates. 



Cuenot interprets the peculiar result as meaning that 

 two gametes both bearing the determiner for yellow are 

 incapable of uniting in fertilisation. The numbers were 



* The discussion of this remarkable case was given in another con- 

 nection at p. 119, but in view of its special importance the facts and 

 argument are repeated here. 



