116 SEXUAL DIMORPHISM 



and mechanical action. His bare yellow oesophagus is in- 

 flated, his neck feathers erected, and his long pointed tail 

 spread out like a fan when he courts. 



We must conclude from these cases that stretching of the 

 skin of the neck by inflation is unfavourable to the growth 

 of feathers, so that the inflated parts of the skin become bare. 

 One reason of this is very probably the expulsion of the blood 

 from the skin caused by the distension. 



The male partridge, Perdix cinerea, Perdix rubra, etc., does 

 not differ much from the female. The cocks are said to fight 

 at the pairing season, but they are monogamous, and conse- 

 quently neither their fighting nor courting are constant occu- 

 pations. The cock partridge is a respectable father of a family. 

 He does not sit on the eggs, but he remains with one mate, 

 and when the brood is hatched continues with his family. 



The grouse, Zagopus scoticus and cdbus, are also monogamous, 

 and sexually monomorphic. 



The Turkey, Meleagris, is placed by recent authorities l in 

 the family Phasianidse, by Claus in 1882 it was joined with 

 the Curassow and Penelope in a distinct family Penelopidae. 

 Whatever its position and affinities, its sexual dimorphism is 

 interesting. The head and neck in all the species are naked 

 and wattled in both sexes, with only a few hair-like feathers. 

 On the forehead is a long fleshy process, which in the 

 ordinary condition is pendulous, and hangs over the base of 

 the beak on one side, but during excitement is erected. In 

 the female this process is present, but much smaller than in 

 the males, and the latter alone possess a large spur. Ogilvie 

 Grant distinguishes three wild species, of which M. gallojiavo, 

 the Mexican Turkey, is the original form of our domestic 

 breeds. In this species the males have an additional peculi- 

 arity, namely, a tassel-like bunch of long, coarse, black, hair- 

 like feathers on the middle of the breast. 



1 "Game Birds," Lloyd's Natural History, London, 1897. 



