BIOLOGY AND AGRICULTURE 



491 



tion. Especially is this true in the case of animal breeding for 

 improved varieties. Here are involved selection, inheritance, 

 and cross-breeding. 



By following well-known biologic methods man can select al- 

 most any group of desirable characteristics and produce a breed 

 possessing them. As evidence of this, note the numerous and 

 widely different types of horse, cow, or dog that man has thus 

 developed. 



In early years England had three general types of sheep, 



FIG. 154. Typical American Merino ewe, a highly specialized breed of 

 sheep, with fine, close-set wool. (After Shaw.) From Kellogg. 



some hornless, some with fine wool, and some producing good 

 mutton. By long and careful breeding and by rejecting all un- 

 satisfactory animals for propagation, they now have several races 

 that combine in a large degree all these useful features. 



In similar ways we have different breeds of cows for different 

 purposes, the Jersey producing as much butter fat as ten ordinary 

 cows, the Holstein for large milk production, and the Hereford 

 for beef. 



