30 WALTER HEAPE. 



It is held by some writers, several of which are quoted by 

 Wiltshire (1883), that the women of various savage tribes 

 exhibit the menstrual flow only at intervals of several 

 months ; and the same author remarks on the fact that girls at 

 puberty in this country menstruate ouly at intervals of three, 

 four, or six months ; and that it may be this condition is an 

 indication of an ancestral habit. Ellis also quotes various 

 authors who state that menstruation takes place at long 

 intervals in women of Lapland, Greenland, the Faroe Islands, 

 Tierra del Fuego, and among the Guaranis of Paraguay. 



The effect of captivity or domestication on the 

 duration of the sexual season in mammals is very re- 

 markable. 



As has been already pointed out, wild sheep have only a 

 very limited sexual season per annum (O. argali, burrhel 

 and poli, in Tibet, Prejevalsky, 1876), a condition which is 

 maintained by the Barbary wild sheep in captivity in this 

 country (Zoo.) ; whereas the domestic sheep has a much 

 longer sexual season, and in addition has for many centuries 

 (Aristotle) been capable of reproducing twice in each year 

 under favourable circumstances. 



Again, the wild goat has a very limited sexual season 

 (Lydekker, 1898), whereas the domesticated goat will receive 

 the male at almost any time (Low, 1845). A more remark- 

 able example is that of certain deer in captivity (Zoo.). Wild 

 red deer have a special sexual season, extending little over 

 three weeks (Bell, 1874), and including certainly not more 

 than two dioestrous cycles; whereas in captivity (Zoo.) the 

 sexual season of these animals extends over most of the year, 

 and consists of an extensive series of dioestrous cycles. 



A similar condition prevails with the wapiti deer in the 

 wild state (Roosevelt, 1893), while in captivity (Zoo.) the 

 possibility of pregnancy at any time of the year is only pre- 

 vented by the fact that the male does not rut during the 

 casting and growth of his antlers ; and it is asserted that 

 park-fed wapiti stags in America are able to beget offspring 

 even after their horns are shed (Caton, 1881). 



