26 HEREDITY. 



ence of domestic species with new dominant characters. We 

 must always remember, that such new dominant characters 

 can be the result of a cross, even if the individuals crossed into 

 the species do not have the character in question, for there is 

 ample evidence for the fact, that very often genes are tr^s- 

 mitted from parent to off-spring during long series of generation, 

 without in any way being factors in the development, without 

 contributing to the qualities of the individuals. The hybrid 

 between two very similar, almost identical sub-species may 

 have a very striking new dominant character. 



The discussion as to the correct way to denote genes in Men- 

 deUan formulae, may be thought to be of very slight import- 

 ance. Nevertheless, the discussion between Plate and one 

 of us, emphasized the difference in our conception of the 

 relation between genes and characters. Mendel simply denoted 

 the genes with wich he was concerned, by the first letters of the 

 alphabet. Following the example of Baur we now do the same, 

 preferring this to the system in use by very many authors, of 

 calhng a gene by a symbol, which calls to mind a character 

 "determined" by it. In the first place, the mnemotechnic 

 advantage is sHght, for whereas it may be easy for Scandi- 

 navian and German readers to remember that S. denotes a gene, 

 which black animals have more than yellow ones, readers of 

 other nationahties would prefer to denote, the same gene by 

 B, Z, N or I. But the chief objection to the system is, that it 

 impUes too much. If we observe that black animals have 

 a certain gene more than yellows, there is no real blackness 

 given in the gene. In different combinations of other genes, it 

 will not produce a difference between yellow and black colour 

 at all, but between cinnamon and agouti, or between cream 

 and pearl-grey, or between champagne and lilac. And very 

 often it will have no colour-modifying influence whatever. 

 There is just as little reason to denote such a gene by a s3mibol 

 recalling the colour black, as there would be to call sulphur B, 

 because copper sulphate is blue. 



We do not want to conclude this chapter without repeating 



