612 MESSRS. J. LEWIS BOXIIOTE AND F. \V. SMALLEY ON 



number of the heterozygons birds largely predoniiiiMtes, and this 

 is probiibly due to the tact that Grizzle x Blue is the commonest 

 form of mating used by breeders to produce Grizzles. 



We have no records of inatings with 2 extrnctetl (Grizzle-bred) 

 Blues, but of Grizzle-bred Blues to Bhio we have ma.de 9 uiatings 

 (Exps. 139-147). These niatings produced 28 birds all Blue in 

 accord.ance with the expectation. 



In order to still further test our hypothesis we have carried out 

 the foregoing experiments (see Table, p. 611). 



The result of a scrutiny of these matings is sufficient to prove 

 the Mendeiiiin inheritance of the Grizzle character. In some of 

 this last batch the expectation was well dehned ; in others — owing 

 to the impossibility of distinguishing homozygous and hetero- 

 zygous birds — the expectation was open to one or two, or in some 

 (rases three, intei-pretaticms. In those cases where the expectation 

 was all Grizzles or Grizzles and absence, in proportion of 3 : 1, and 

 oidy Grizzles were produced, we have concluded that one of the 

 parents, at least, was homozygous— similarly, if any of the pro- 

 geny in those cases lacked the Grizzle, we have presumed that 

 the expected result should have been 3:1. On this basis we 

 have tested the results and we find : — 



No. of 

 Ex)ieotMtioii. Matings. Result. 



All Grizzles 7 39 Grizzles. 



3:1 7 32 Grizzles, 11 absence of Grizzle, 



E pinlity 3 9 Grizzles, 9 absence of Grizzle, 



No Grizzles 2 18 absence of Grizzle. 



Equality or 3 : 1 2 5 Grizzles, 1 absence of Grizzle. 



This last set of matings places therefoi'e beyond doubt the 

 Mendeliau inheritance of the Grizzle charactei'. 



In the summary given above we have, however, left out 

 Exp. 180, in which with an expectation of 3:1 or all Grizzles, 

 14 Grizzles and one pure Blue were produced. At the present 

 moment, we can offer no reason for this considei-able deviation 

 from the expected result. 



Grizzles and Chequers. 



The Grizzle character is dominant to the Chequer, although, 

 in almost every case, the heterozygotes may be e;vsily recognised. 



To test this inheiita.nce we have made the following matings 

 (see Table, p. 613). 



These matings show fairly clearly the mode of inheritance, 

 but from the smallness of the numbers the proportions of the 

 different colours are not always in exact accoixhince with the 

 expectation. It may be further noted that although, from the 

 above reason, certain expected colours have as yet not occurred, 

 on the other hand no unexpected colours or combinations have 

 appeared. Thus we see that in Experiments 200 & 201 the 

 recessive Chequers gave us, as expected, 14 Chequers to 4 Selfs, 

 and no Grizzles ; in Experiments 202 k. 205 the pure Grizzles 

 gave us, 11 Grizzles to 1 Self, and no Chequers. These two latter 



