I02 MENDELISM chap. 



are concerned has been recently worked out in 

 poultry. The Silky breed of fowls is characterised 

 among other peculiarities by a remarkable abundance 

 of melanic pigment. The skin is dull black, while 

 the comb and wattles are of a deep purple colour 

 contrasting sharply with the white plumage (PI. 

 v., 3). Dissection shows that this black pigment 

 is widely spread throughout the body, being especially 

 marked in such membranes as the mesenteries, the 

 periosteum, and the pia mater surrounding the brain. 

 It also occurs in the connective tissues among the 

 muscles. In the Brown Leghorn, on the other 

 hand, this pigment is not found. Reciprocal crosses 

 between these two breeds gave a remarkable differ- 

 ence in result. A cross between the Silky hen and 



Silky Brown Leghorn ^^ E^°^" Leghorn 



# X * cock produced F^ birds, 



I in which both sexes 



exhibited only traces 



«f G? C? 



? X ^ F, of the pigment. On 



casual observation they 

 ~L X 1 T, might have passed for 

 ^ unpigmented birds, for 

 ^'^- "9- with the exception of 



Scheme illustrating the result of crossing a • 1 n 1 r 



Silky hen with a Brown Leghorn cock. ^^ OCCaSIOnal lleCK 01 

 Black sex signs denote deeply pigmented ■ 4. 4. 1_ ' 1 * 



birds, and light sex signs those without plgmCnt tuelr SKlU, 

 pigmentation. The light signs with a t- J j.^! 



black dot in the centre denote birds with COmb, and WattlCS WCrC 

 a small amount of pigment. 1 • j.i t» 



'^^ as clear as m the Brown 



Leghorn (PL V., i and 4). Dissection revealed the 

 presence of a slight amount of internal pigment. 

 Such birds bred together gave some offspring with 

 the full pigmentation of the Silky, some without any 

 pigment, and others showing different degrees of 



