136 Melanic Types [cii. 



apparently true of the yellow fruits, as compared with the 

 red fruits of their corresponding types, and of the yellow 

 flowers of some Composites {e.g. Ge7^bera) ^. 



In many types of flowers, e.g. Stocks, Primula, Sweet 

 Pea, the very dark and more fully-coloured varieties are 

 regularly recessive to the less dark types, whether purple or 

 red. The same will almost certainly be proved for Cycla- 

 men, Rose, Hollyhock, Dahlia, Carnation, Sweet William, 

 and many more. In Antirrhinum Miss Wheldale finds that 

 among magentas the darker are recessive to the common 

 colours, but among the crimsons or reds the darker are 

 dominant to the lighter. 



The difficulties which preclude general statements in 

 regard to the genetic relations of melanic types among 

 animals have been illustrated in much that has gone before. 

 The loose description ''melanic varieties," common in the 

 writings of systematists, covers a number of phenomena 

 essentially distinct. For example there are melanic forms 

 which owe their greater blackness to the presence of some 

 dominant factor responsible for a greater deposit of black, or 

 at least dark, pigment. In Fowls, for instance, black is at 

 least partially dominant over the bmikiva colour which 

 fanciers call " Black-red." The dark brown variety called 

 " Brown-breasted" is similarly a dominant. In Pigeons, as 

 Staples-Browne has proved, black is dominant to the blue 

 of the wild type. In the Horse the presence of black, as in 

 bays and browns, is dominant over the absence of blacks as 

 in chestnutst. 



On the contrary in Rabbits, Rats, Mice, &c. the black 

 variety is produced by the omission of the agouti-factor, G, 

 from the wild type, and black thus is apparently a recessive. 

 Even here however the presence of black pigment is 

 dominant to its own absence. It would be interesting to 

 know to which group the Cat belongs. 



In Insects again no rule of universal application to 



* That in Tomato yellow fruit is recessive to red was established by 

 Hurst (160, p. 115). The case of Gerbera is given on the evidence of 

 crosses made by Mr R. I. Lynch between red Gerbera Jainesoni and the 

 yellow-flowered variety " Sir Michael." 



t The genetic relation of the totally or self-coloured black to the other 

 horse-colours is not yet known. 



