F. Pitt 291 



never been the subject of selection, our breeders not regarding it as of 

 any importance. In certain countries, Jamaica for one, cattle with 

 pigment round the eyes are actually preferred on account of their 

 supposed immunity to the attacks of flies and certain eye diseases. As 

 far as English flies are concerned they certainly bite the eyes of red- 

 eyed quite as badly as white-eyed Herefords, and I have been unable to 

 see that the presence or absence of colour makes the least difference. 

 However as some buyers for export choose red-eyed cattle the character 

 has after all a certain interest for the breeder. 



The coloured area varies from a comparatively large circle of red 

 round each eye (PI. VII, figs. 5 and 6) to the merest trace of pigment 

 on one eye (PI. IX, F). It is not uncommon for one eye to be well marked 

 and the other plain (PI. IX, C). When this is so, and in cases where only 

 a little pigment is present round each eye, we have apparently expressions 

 of the heterozygous condition. 



The accompanying diagrams (4 and 5) show that the presence of 

 pigment round the eyes is dominant to its absence, segregation following 

 the simple Mendelian ratio. But dominance is not so complete as, for 

 instance, in the classical case of the round and the wrinkled pea, and, as 

 mentioned above, heterozygotes generally betray their constitution by 

 the reduced amount of pigment present. 



The character appears to segregate independently of other pigmen- 

 tation factors, for I have seen very white cattle with red eyes, and very 

 dark ones with white eyes ; but it is possible that the red-eyed factor 

 can only reach its full somatic expression when in company with that 

 for extension of pigment, and that the factor for normal colouration 

 inhibits its full development. This is suggested because specially 

 heavy pigmentation round the eyes has been chiefly met with in company 

 with absence of white from Jbhe neck. Out of 18 dark-necked cattle 14 

 had red eyes, of which 3 had conspicuous pigmented rings round their 

 eyes, but one very red-eyed calf had a fair amount of white on the neck. 

 The examination of the 1 10 cattle already referred to gave the following 

 figures : 



56 normally marked Herefords with red eyes 

 14 dark-necked with red eyes 



3 very white with red eyes 



Total ... 73 red-eyed cattle 



28 normally marked white-eyed cattle 



4 dark-necked white-eyed ones 



5 excessively white and with wliite eyes 



Total ... 37 white-eyed Herefords 

 Jouru. of Gen. ix 19 



