230 THE DESCENT OF MAN. 



size, can be felt, or even seen, at birth or soon afterwards.-" Our 

 rule, however, seems to fail in some breeds of sheep, for instance 

 merinos, in which the rams alohe are horned; for I cannot find 

 on inquiry," that the horns are developed later in life in this 

 breed than in ordinary sheep in which both sexes are horned. But 

 with domesticated sheep the presence or absence of horns is not a 

 firmly fixed character; for ^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 protuber- 

 ances so common on the heads of birds,'" and he comes to the fol- 

 lowing conclusion; — that with those species in which they are con- 

 fined 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 con- 

 firmation 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 pheas- 

 ant (Crossoptilon auritum), however, offers a remarkable excep- 

 tion, for both sexes possess the fine cau"'al plumes, the large ear- 

 tufts and the crimson velvet about the head; I find that all these 

 characters appear 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 



*^ I have been assured that the horns of the sheep in North Wales 

 can always be felt, and are sometimes even an inch in length, at 

 birth. Toiiatt says ('Cattle,' 1S34, p. 277), that the prominence of the 

 frontal bone in cattle penetrates the cutis at birth, and that the 

 horny matter is soon formed over it. 



" I am g-reatly indebted to Prof. Victor Carus for having made 

 inquiries for me, from the highest authorities, with respect to the 

 merino sheep of Saxony. On the Guinea coast of Africa there is, 

 however, a breed of sheep in which, as with merinos, the rams alone 

 bear horns: and Mr. Winwood Reade informs me that in one case 

 observed by him, a young ram, born on Feb. 10th, first showed horns 

 on March 6th, so that in this instance, in conformity with rule, the 

 development of the horns occurred at a later period of life than in 

 Welsh sheep, in which both sexes are horned. 



■" 'Ueber die knochernen Schadelhocker der Vogel' in the 'Nleder- 

 landischen Archiv fur Zoologie,' Band I. Heft 2, 1872. 



" In the common peacock (Pavo cristatus) the male alone possesses 

 spurs, whilst both sexes of the Java Peacock (P. muticus) offer the 

 unusual case of being furnished with spurs. Hence I fully expected 

 that in the latter species they would have been developed earlier io 



