310 THE DESCENT OF MAN 



steep the presence or absence of horns is not a firmly fixed 

 character; for a certain proportion of the merino ewes bear 

 small horns, and some of the rams are hornless ; and in most 

 breeds hornless ewes are occasionally produced. 



Dr. W. Marshall has lately made a special study of the 

 protuberances so common on the heads of birds," and he 

 oomes to the following conclusion: that with those species 

 in which they are confined to the males they are developed 

 late in life; whereas with those species in which they are 

 common to the two sexes, they are developed at a very 

 early period. This is certainly a striking confirmation of 

 my two laws of inheritance. 



In most of the species of the splendid family of the 

 Pheasants, the males differ conspicuously from the females, 

 and they acquire their ornaments at a rather late period of 

 life. The eared pheasant {Grossoptihn auritum), however, 

 offers a remarkable exception, for both sexes possess the 

 fine caudal plumes, the large ear-tufts, and the crimson 

 velvet aboiit the head; I find that all these characters ap- 

 pear very early in life, in accordance with rule. The adult 

 male can, however, be distinguished from the adult female 

 by the presence of spurs; and, conformably with our rule, 

 these do not begin to be developed before the age of six 

 months, as I am assured by Mr. Bartlett, and even at this 

 age the two sexes can hardly be distinguished.'* The male 

 and female peacock differ conspicuously from each other 

 in almost every part of their plumage, except in the elegant 

 head-crest, which is common to both sexes; and this is 



•" "ITeber die knocherneii Schadelhooker der Vogel, " in the "Niederland- 

 ischen ArchiT filr Zoologie," Band I. Heft 2, 18t2. 



*• In the common peacock (Pavo crisiatus) the male alone possesses spurs, 

 ■while both sexes of the Java peacock {P. muiicas) offer the unusual case- of 

 being furnished with spurs. Hence I fully expected that in the latter species 

 they would have been developed earlier in life than in the common peacock; 

 but M. Hegt of Amsterdam informs me that with young birds of the previous 

 year, of both species, compared on April 23, 1869, there was no difference in 

 the development of the spurs. The spurs, however, were as yet represented 

 merely by slight knobs or elevations. I presume that I should have been 

 Informed if any difference in the rate of development had been observed 

 subsec|.uently. 



