MENDELIAX BXPERIMEXTS WITH FOWLS. 243 



were either destitute of pigmentation or showed only a small 

 amount of it in certain parts. But when the opposite cross was 

 made, Silky co^k with J3rown Leghorn hen, the F, males had 

 unpigmented skins, while the females were almost as much pig- 

 mented as the pure Silky hens. Bateson explains these results 

 l)V the assumption that there are three pairs of characters or 

 allelomorphs att'ecting the results, namely : — - 



Presence and aV)sence of femaleness. 

 Presence and absence of the black pigmentation. 

 Presence and absence of a factor which can suppress or 

 mask the development of the pigmentation. 



He assumes that this last factor is double or homozygous in the 

 Brown Leghorn cock, single or heterozygous in the Brown Leghorn 

 lien, and absent in the Silky. There is no need for such assump- 

 tions in the case of the Bankiva cock, but it must be noted that I 

 have no experience of the opposite cross, Bankiva hen with Silky 

 cock. 



In the experiment here considered the white colour of the 

 Silky plumage is perfectly recessive. This resvdt also differs 

 somewhat from that of pi'evious experiments. Davenport crossed 

 a Silky cock with Frizzled hens, but he states that the coloiu- of 

 Frizzles is not constant Ijiit variable. His hens were of various 

 colours — dark brown, yellowish, light brown, and mixed black 

 yellow and red. Some of them may have been carrying white as a 

 recessive. Of his F, hybrids 7 were white and 25 coloured. 

 iJavenport considers that the results <lo not agree with either the 

 hypothesis that white is recessive or that it is dominant. He con- 

 cludes that the white is not always dominant, but this seems to be 

 a slip : he proljably means that the colour is not always recessive. 



Bateson found that the white of the Silky, tliough recessive to 

 colour, gave coloured offspring when crossed with ceiiain other 

 recessive whites obtained from crossings. He concludes, there- 

 fore, that the whiteness of the Silky is due to the absence of one 

 of two elements which together produce colour. We shall have 

 to consider this point again in discussing the colours of the F^'s 

 which form the point of chief interest in my results. 



We now come to the consideration of the F^ generation, that 

 is of the chicks which I have hatched and reared from the pair 

 of F,'s above mentioned. The first brood was hatched on May 1 .5th, 

 1911, and consisted of nine chicks, one of which died within the 

 first few days ; the othei- eight are still alive and vigorous. The 

 hen afterwards sat again, but this time hatched only two chicks, 

 probably in consequence of the very dry weather; these two 

 were hatched in August. The following table (p. 244) shows the 

 characters of these chickens. 



The numbers of these specimens ai'e, of course, too small to 

 afford evidence of any importance with regard to the numerical 

 proportions in which the characters or combinations of characters 



16* 



