318 



LAWS OF VARIATION. 



Chap. XXV. 



in correlation with tiie elongated and reversed feathers on the 

 back of the neck, which form the hood. 



The hoofs and hair ai'e homologous appendages; and a 

 careful observer, namely Azara,^^ states that in Paraguay 

 horses of various colours are often born with their hair curled 

 and twisted like that on the head of a negro. This peculiarity 

 is strongly inherited. But what is remarkable is that the 

 hoofs of these horses " are absolutely like those of a mule." 

 The hair also of their manes and tails is invariably much 

 shorter than usual, being only from four to twelve inches in 

 length ; so that curliness and shortness of the hair are here, 

 as with the negro, apparently correlated. 



With respect to the horns of sheep, Youatt ^^ remarks that 

 " multiplicity of horns is not found in any breed of much value; 

 " it is generally accompanied by great length and coarseness 

 " of the fleece." Several tropical breeds of sheep which are 

 clothed with hair instead of w^ool, have horns almost like 

 those of a goat. Sturm ^^ expressly declares that in different 

 races the more the wool is curled the more the Lorns are 

 spirally twisted. We haA^'e seen in the third chapter, where 

 other analogous facts have been given, that the parent of the 

 Mauchamp breed, so famous for its fleece, had peculiarly 

 shaped horns. The inhabitants of Angora assert ^* that " only 

 " the wdiite goats wdiich have horns wear the fleece in the 

 " long curly locks that are so much admired; those which 

 " are not horned having a comparatively close coat." From 

 these cases we may infer that the hair or wool and the horns 

 tend to vary in a correlated manner. ^^ Those who have tried 

 hydropathy are aware that the frequent application of cold 

 water stimulates the skin ; and whatever stimulates the skin 



'^ < Quadrupedes du Paraguay,' 

 torn. ii. p. 333. 



12 On Sheep, p. 142. 



*2 ' Ueber Kacen, Krouzungen,' &c., 

 1825, s. 24. 



^* Quoted from Conolly, in ' The 

 Indian Field,' Feb. 1859, vol. ii. p. 

 266. 



** In the third chapter I have said 

 that " the hair and horns are so close- 

 ly related to each other, that they arc 



apt to vary together." Dr. Wilckens 

 ("Darwin's Theorie," 'Jahibuch 

 der Deutschen Viehzucht,' 1866, 1. 

 Heft) translates my words into " lang- 

 und grobhaarige Thiere sollen ge- 

 neigter sein, iange und viele Horner 

 zu bekommen," and he then justly 

 disputes this proposition ; but what I 

 have really said, in accordance with 

 the authorities just quoted, may, I 

 think, be trusted. 



