666 



THE AMERICAN NATURALIST [Vol. LI 



Mansell (12) reports 168 per cent, of lambs in 11,668 

 English Shropshires in 1896, while Humphrey and Klein- 

 heinz (6) from figures on the University of Wisconsin 

 flock made the following breed comparisons : 



TABLE IV 





























Dorset 



Oxford".".".'.;;;.;; 



Hampshire 



27 



23.7 

 .",3 3 





120 





15 



3 



9.5 



13.6 



Percentage of lambs as given by Mansell is, of course, 

 only a rough indication of twin-bearers, since ewes having 

 triplet and quadruplet births may be included. 



Eietz and Roberts (13) show that 43 out of every 100 

 births in American Shropshires are multiple births, while 

 they have determined from Heape's (5) statistics of 

 1895-96 that 64 out of every 100 births in English Shrop- 

 shires are multiple. 



Plumb (12) found in 20,037 Shropshire births 59.2 per 

 cent, were singles, 39.2 per cent, twins, and 1.3 per cent, 

 triplets, all recorded in the American Shropshire Flock 

 Book, 1890 to 1899. 



Heape (5), from a study of the birth records of 89,000 

 ewes in English flocks, presents the following data to 

 show the relative fertility of different breeds of sheep: 



TABLE V 



Kent 124.05 31.38 



Southdown 109.89 18.67 



Ilampphiro 114.69 24.09 



Oxford Down 119.16 35.02 



Dorset Horn 123.63 37.55 



Shropshire 136.79 46.84 



