;W4 AGRICULTURE. 



II. Improvement. 



As time went on people became more civi- 

 lized. Their habits, customs, ambitions and 

 demands changed. With this change in the 

 people themselves many changes in domestic 

 animals followed, as a natural consequence. It 

 was a general change in the direction of im- 

 provement, although this was not always the 

 case. 



There are three natural laws which are great 

 factors in affecting animal form and character 



> 



in its reproduction, and make change possible. 

 They are 



1. Heredity. 



2. Variation. 



3. Selection. 



III. Heredity. 



Ribot defines heredity as " that biological law 

 by which all living beings tend to repeat them- 

 selves in their descendants." This is the law 

 which makes possible the resemblance between 

 a parent and offspring, and is well expressed in 

 the common saying that " like produces like." 

 It is this principle upon which we depend 

 for the transmission of milk-producing quali- 

 ties in dairy cattle, speed in race-horses, etc., 

 and by which we are able to maintain a 

 standard of breed, characteristics or type in 

 animals. 



