300 ELEMENTS OF GENERAL SCIENCE 



would probably, even in its second year, be more conspicuous 

 for its weeds than for its corn. Farm animals, if left to shift 

 for themselves, would doubtless, in most cases, soon cease to 

 exist or would rapidly change their habits and appearance. 

 A poultry yard, if deserted by man, would soon be cleared of 

 chickens by marauding animals, by disease, or by starvation. 

 A rose garden requires constant care to prevent its losing 

 the high type of flower production desired by man. An apple 

 orchard under relaxation of care very soon becomes infested 

 by disease and reverts to relative non-productivity. Man's 

 artificially selected types are in a condition of high tension, 

 which is soon relaxed, partly or wholly, when man ceases to 

 select and to care for his selected types. 



326. Inheritance. Much that has been said bears more or 

 less directly upon the topic of inheritance. " Heredity is the 

 rule of persistence among organisms." It is an old saying 

 that "like begets like," and while we know that organisms 

 vary from one generation to another, we also know that they 

 resemble one another with varying degrees of resemblance. 

 We expect individual characteristics of parents to be more or 

 less represented in the individual characteristics of offspring. 

 Francis Gal ton studied in a large number of families the rela- 

 tions between the average height of the parents and the aver- 

 age height of the adult children, and some of these relations 

 appear in the following table : 



Average height Average height 



of parents of children 



72.5 71.4 



71.5 69.9 



70.5 69.5 



69.5 68.6 



68.5 68.0 



67.5 67.6 



66.5 67.1 



65.5 66.8 



64.5 65.6 



