friLoufi rxiiKRii'AXfi-: rx iTfMcox.s. (505 



From these matings we see that : — 



(i) Silver to Silver (Exps. 148 to 151) giv^es notliing but Silver, 

 according to expectation. 



(ii) Blue to Silver (Exps. 152 to 159) should give nothing hut 

 Blues or Blues and Silvers according to whether the Blues 

 are heterozygous or not, and wesee thatwhen our knowledge 

 of the gametic formulae of the parents was known for cer- 

 tain, the results were in exact accord with expectations, and 

 no results antagonistic to possible expectation8 occurred, 



(iii) Heteroz3^gous Blues to Silvers (Exps. 160-163) should give 

 equality of Blues and Silvers. In the case of Exp.s, 160 and 

 161 no Silvers appeared, but the numbers bred were very 

 small. In the other experiments, exact equality was 

 reached, so that we may well assume tliat a continuation of 

 the other experiments would have led to the appearance 

 of so)ne Silvers, 



(iv) Heterozygous Blue X Heterozygous Blue should give Blues 

 and Silvers in pi-oportion of 3:1, which was the exact 

 result of this mating (Exp. 83). 



The results therefore show clearly that Silver is recessive to 

 Blue. The arguments showing that the diffei'ence between these 

 colours is one of concentration and dilution (rather than a differ- 

 ence of the colour factor itself), depend on the study of this 

 dilution factor, which, as it concerns the inheritance of other 

 colours and shades, not dealt witli in this paper and at pre.seut 

 only imperfectly understood, is best defexred for the present. Its 

 discussion in no way affects the proof of the dominance of Blue 

 over Silver. 



C/ieque7'ing. 



Chequering is dominant to pure colour. It is difficult to 

 realize therefore how it can have originated, since the typical 

 wild pigeon shows no such markings. At the present time, 

 however, in many parts of the country wild birds show 

 chequering, but it seems more than likely that in these cases the 

 marking has been introduced by a cross with the domestic bird, as 

 most of the Wild Rocks in this country are now intermixed with 

 feral ones. Once this cross had been effected the chequering would 

 of cour.se frequently show itself. 



In direct contradiction to the foregoing remarks the following 

 fact is worth noting. Some years ago a pair of pure wild birds 

 was taken by one of the authors from a remote district in the 

 "West of Ireland. All the wild pigeons seen (and there were no 

 tame ones within a radius of at least 30 miles) were purely typical 

 Blue Bocks. This pair bred in an aviary for five or six seasons, 

 producing only typical wild birds like themselves. Two seasons 

 ago (in 1909) an attempt was made to establish some of their 

 progeny as semi-wild bii"ds and they were allowed to fly at liberty 

 from a dove-cot. One pair remained and reared several young, one 

 of which proved to be chequered ! 



Proc. Zool. Soc— 1911, No. XLIH. 43 



