610 MESSRS. J. L2WIS BOXHOTE AND F. AV. SMALLEY ON* 



In only 8 of the other matings did Bhies fail to appear, and 

 Ave may therefore consider that Tvhen they did appear the 

 expectation should have been equality as before. Deducting 

 therefore these 8 matings which only produced Grizzles, we have 

 left 33 matings producing 156 young. 63 being Grizzles and 

 93 Blues. Since only one expectation is possible if both colours 

 appear, we ai-e justified in uniting the tiguies from these two sets 

 of matings and treating them together. We find, therefore, that 

 in the total we have 52 matings of Grizzle to Blue, which produced 

 220 young of which 100 were Grizzles and 120 Blues; and this 

 proportion, although not exact, is not unreasonably far from the 

 expectation (Equality), and certainly seems to show a Mendelian 

 basis of inheritance. 



If we digest the facts still further, we find that actual equality 

 was reached in only 19 cases, and this by including the odd 

 numbered broods where the deviation was not more than one. 



We have, therefore. 



Actual Equality reached in roughly 36 ~ '^ of the 



matings. 

 Blues outnumbered the Grizzles by more than one in 20' - ., 

 Grizzles ,, ,, Blues ,, „ 14= ^ ,, 



Blues only, appeared in IS"/^ ,, 



G lizzies only, .. „ 14"^ .. * 



This, therefore, seems to show that while only a moderate 

 percentage of matings gave the exact Mendelian expectation, the 

 variation to one side or other of the mean is fairly evenly balanced, 

 Avitli however a slight but unmistakable tendency towards an 

 o\erproduction of Blues : a tendency which was also shown in 

 the Grizzle to Grizzle matings. 



Thus, as in the case of the Chequers where we found the 

 Mendelian proportions fairly well maintained, but with a distinct 

 tendency to an ovei-production of Chequers, so also in the Grizzles 

 Ave see a similar tendency to an overproduction of Blues. 



There remains for considei-ation the 8 matings in Avhich only 

 Grizzles appeared. Two of these may be at once dismissed as 

 only one bird was reared, so that Ave haAe no hint as to the 

 probable expectation. From the other 6 matings 25 birds were 

 reared, so that there is a reasonable probability of a Blue having 

 appeared were either of the parents heterozygous. Unfortunately 

 for the simplicity of this reasoning, we find on investigating the 

 matter more closely that although in 3 of these matings the 

 same hen was used and we might therefore presume her to be 

 homozygous, yet by her progeny in another mating (Exp. 109) 

 she proved herself to be heterozygous. This then leaA-es only 3 

 cases out of 60 in Avhich the Grizzle parent might be homozygous. 

 So that again, just as we found in the Chequers and Blues an 

 overwhelming pioportion of homozygous birds, which we attributed 

 to the unconscious selection of breeders, similarly in this case the 



* This last ealcniation is of course exclnsive of the 8 matinars mentioned above, 

 ill which the gametic formula of the Grizzle parent was doubtful. 



