Chap. XVIII. DEVELOPMENT OF HAIR. 281 



duction. He gives, however, only a conjectural and 

 unsatisfactory explanation of its use.^^ 



In most cases, when daring the breeding-season the 

 male alone emits a strong odour, this probably serves 

 to excite or allure the female. We must not judge 

 on this head bv our own taste, for it is well known 

 that rats are enticed bv certain essential oils, and 

 cats by valerian, substances Avhich are far from agree- 

 able to us ; and that dogs, though they will not eat 

 carrion, sniff and roll in it. From the reasons given 

 when discussing the voice of the stag, we may reject 

 the idea that the odour serves to bring the females 

 from a distance to the males. Active and long-continued 

 use cannot here have come into play, as in the case of 

 the vocal organs. The odour emitted must be of con- 

 siderable importance to the male, inasmuch as large 

 and complex glands, furnished with muscles for evert- 

 ing the sack, and for closing or opening the orifice, 

 have in some cases been developed. The development 

 of these organs is intelligible through sexual selection, 

 if the more odoriferous males are the most successful in 

 winning the females, and in leaving offspring to inherit 

 their gradually-perfected glands and odours. 



Developnent of the Hair. — We have seen that male 

 quadrupeds often have the hair on their necks and 

 shoulders much raore developed than in the females; 

 and many additional instances could be given. This 

 sometimes serves as a defence to the male durinor his 

 battles; but whether the hair in most cases has been 

 specially developed for this purpose is very doubtful. 

 We may feel almost certain that this is not the case, 



12 Pallas, ' Spicilegia Zoolog.' fasc. xiii. 1799, p. 24 ; Desmoulins, 

 ' Diet. Class. d'Hist. Nat.' torn. iii. p. 586. 



