40 THE SHEEP AND ITS COUSINS 



to 150 days in merinos;^ hybrids between the two 

 being intermediate in this respect. In some of 

 the Tibetan and Himalayan breeds the period is 

 extended, according to Mr. Brian Hodgson,^ to no 

 less than 160 days. 



In this connection it may be noted that whereas 

 the Tibetan breeds, and in a somewhat less degree 

 the merino, are but little modified, or, in other 

 words, generalised types of sheep, the Southdown 

 is a highly modified or specialised breed, which 

 comes to maturity at a very early age. This being 

 so, it would be quite natural to expect that the foetal 

 life of that breed should be shortened. 



Analogous variations occur in the relative degree 

 of fertility of the various breeds, some usually pro- 

 ducing only a single lamb at a birth, while others 

 commonly produce twins or even triplets. Among 

 British breeds the Shropshire is noted for its 

 fecundity, sometimes producing four or even five 

 lambs at a birth, but the most fruitful of all appears 

 to be the earless Shanghai breed, of which a small 

 flock was exhibited in the London Zoological 

 Gardens in the year 1857. These, according to 

 Mr. A. D. Bartlett,* bred twice in a year and pro- 

 duced four or even five lambs at a time ; three ewes 

 having given birth to no less than thirteen lambs 



* Darwin, op. cit., p. loi. 



* Journ. Asiat. Soc. Bengal, vol. xvi. p. loio. 



* Proc. Zool. Soc. London, 1857, p. 105. 



