186 Peculiar Pigmentation of the Silky Fowl 



tissues of the body. Seen through the thin epidermis this pigment 

 gives the bird the appearance of a fowl with a black skin, deep purple 

 comb and wattles, and dark slaty shanks. The iris is heavily pigmented, 

 and the usually white earlobe takes on a more or less intense turquoise 

 tint which is especially noticeable in the hens. The somatic peritoiieum, 

 the periosteum and pia mater are inky black from the pigment with 

 which they are crowded. The splanchnopleure is much less pigmented, 

 and the liver seen through this looks its normal colour. The muscles 

 also have a blackish appearance, but we have not made any histological 

 examination to determine the exact distribution of the pigment here. 

 It is apparently confined to membranes of mesodermal origin, and is 

 absent from the lungs, liver and other viscera, while at the same time 

 the plumage is white. There is never any trace of it in the allantois, 

 or other foetal membranes. 



Our experiments with this breed were begun with the idea of 

 investigating the nature of the form of comb by which it is characterised, 

 but we had not proceeded far before it became evident that the in- 

 heritance of the peculiar pigmentation promised more interesting and 

 novel results. As the case presents features unlike any hitherto met 

 with elsewhere it will be convenient if we give a brief outline of the 

 main results and of the interpretation before passing to a detailed 

 examination of the experimental data. 



General statement of results. 



The breed with which the Silky was originally crossed was a strain 

 of Brown Leghorns which had been in our possession since 1899. The 

 first indication of something unusual was the definite difference found 

 in the reciprocal crosses between these two breeds. While the mating 

 of Silky % X Brown Leghorn j/* resulted in chicks of both sexes with 

 little pigmentation, the mating of Brown Leghorn $ x Silky f^ gave 

 a markedly different result. From this mating the (/• chicks had only 

 a little pigment and were indistinguishable from those resulting from 

 the previous cross, but the % chicks were all deeply pigmented, differing 

 but little in this respect from a pure Silky ^ On breeding the F^ birds 

 together there resulted in either case an F2 generation consisting of 



1 The Fi chicks all had coloured plumage and subsequent breeding showed that the 

 white of the Silky behaved as a simple recessive (cf. Rep. Evol. Comm. Roy. Soc. iv. 1908). 

 Our experiments have led us to infer that the pigmentation is quite independent of the 

 colour of the plumage. 



