84 



EVOLUTION AND ANIMAL LIFE 



At this point we may conceive that (2) conscious selection of 

 the more desirable individuals appears. Through its agency, 

 Hampshire, Shropshire, Cheviot, and Southdown sheep alike, 

 and the others in their degree, tend toward larger size, more 

 wool, plumper bodies, earlier maturity, greater docility, greater 

 fertility, or whatever virtues the average shepherd may prize in 

 a sheep. While in race traits, the breeds (uncrossed) tend to 

 diverge from one another, in these adaptive qualities, their 

 tendency is to run parallel or even to converge toward greater 

 resemblance. 



With conscious selection (3), there is first a tendency to 

 emphasize the qualities of desirable breeds. If, for example, 



FIG. 50. Typical Southdown ewe. (After Shaw.) 



the Hampshire is a favorite breed, the individuals showing most 

 distinctly black ears, legs, and face will be preferred by breeders 

 to those having these parts pale. Again, new points of special 

 excellence will appear in the breed and these will be deliberately 

 emphasized, and perhaps by continuous selection a new breed 

 will be formed having one or more of these as a distinctive trait. 

 According to Somerville, one may chalk out on a wall any 

 form or type of sheep he may like, and then in time reproduce 

 it through selective breeding. 



In Nova Scotia, Mr. A. Graham Bell has developed a new 

 breed of sheep by selection, its distinctive character being in the 

 increased milk flow, with an increased number of teats. 



