n] Colours of Animals 43 



The black body-pigmentation of the Silky is a dominant, but may be 

 inhibited by another factor, the descent of which is sex-limited. See Chap. x. 



Another sex-limited descent is to be found in the relations of Cuckoo 

 to black, but the details have not been ascertained (Spillman, 249, 253, a). 



The daw-eye is recessive to red. The dark iris is usually a dominant 

 to red. 



Red ear-lobe is an imperfect dominant to white. R.E.C. (19). 



Principal papers dealing with these features are R.E.C. (19-22), 

 Hurst (156); Davenport ( 10 1). 



Pigeons. 



Black is dominant to blue. Relations of red and yellow not clear. 

 Black and blue are dominant to white of Fantail ; heterozygotes generally, 

 if not always, having some white. Chequering dominant to its absence. 

 The white rump of the Rock-pigeon is dominant to blue rump (Staples- 

 Browne, 255). 



Canaries. 



Presence of black, as in green and pied types, dominant to absence of 

 black as in the various yellows and cinnamons. The pink eye of cinnamons 

 is recessive to black eye, with a sex-limited inheritance. There are probably 

 several heterozygous colours, but in order to determine these the genetic 

 interrelationships of the various Yellows, Jonque, Mealy, must be worked 

 out. The " cap " and lacing of the Lizard are dominants. (Noorduijn, 

 213-5; Davenport, 105; F. M. Durham, unpublished.} 



Axolotl. 



Crosses between normal and albino gave dominance of pigmentation. 

 Subsequent generations showed remarkable and as yet unique features. In 

 F 2 dark larvae to white larvae were 3:1; but the white F* larvae, though 

 remaining red-eyed, acquired a certain amount of pigment, sometimes 

 distributed as a metameric chequering. No thorough albino occurred in F*. 

 When however these chequered albinos were bred with a true albino, the 

 latter was found dominant and true albinos were produced (Hacker, 

 143-4). Hacker compares this case with the phenomena seen in Mice, 

 &c., but there is an essential distinction in the fact that in all other 

 instances true albinos come in F^ and in the dominance of the true 

 albinism over the chequered character. It would be interesting to see 

 whether the development of pigment in the F. 2 whites is in any way 

 dependent on conditions. 



LEPIDOPTERA. 



Bombyx mori (Silkworm). Brown colour seen in a dark variety of the 

 moth was proved to be an imperfect dominant (Coutagne, 83, p. 122). 



The larvae have many colour-types. Coutagne used a dark "moricaud" 

 variety, a variety with transverse stripes, and ordinary white larvae. Both 

 the coloured types are dominant to white, but when the dark self-colour 

 factor and the stripe-factor are present in the same larva the stripes show 

 on the dark ground-colour (ibid. p. 142). Toyama (268) also made many 

 experiments with the colours of the larvae. He found striping a dominant 

 over plain white. In certain F families from striped x white a new pale 



