VARIETIES, STRAINS, AND SPORTS. 319 



India; also the peculiar color patterns of the fishes in cer- 

 tain regions of northern Georgia. 



Varieties or subspecies, are subdivided into races, and 

 the latter into strains. The term hreed is confined to 

 the offspring of some single indiyidual or pair in the 

 case of man and the domestic animals, such as the breed 

 of ti'otting horse, individuals of whicli breed true if not 

 contaminated by mixture with mongrel stock or indiyiduals 

 of another breed. 



A strain is the least recognizable variation from a certain 

 given normal specific or racial form. Among horses we 

 have, for example, the Hambletonian or Morgan strain, and 

 in human families the house of Hapsburg with its distinc- 

 tive physical trait. A single distinguished individual may 

 impress certain mental and physical characteristics which 

 may be transmitted more or less continuously through 

 several or many generations. 



A sport is the result of the appearance at birth of a sud- 

 den and often very marked character. It occurs most 

 commonly in cultivated plants and rarely in domesticated 

 animals. Sports in plaTits can be propagated by grafts, off- 

 sets, etc., and sometimes by seeds. Example of a sjjort in 

 animals is the otter sheep. Sports may lead to the forma- 

 tion of f)ermanent varieties, species, or genera, but they are 

 generally " swamped " or disappear by intercrossing. 



Variation is not always, if ever, fortuitous, but deter- 

 mined by determinate physical and biological conditions of 

 the environment along certain determinate lines. Where 

 variations have been useful they have survived, and where 

 useless have been swamped by intercrossing or have dis- 

 appeared by disease. The best examples of this are the 

 winged insects and the birds, which, derived from terrestrial 

 creeping ancestors, have, probably as the result of the 

 struggle for existence and the overcrowding of the earth, 

 evolved wings by which they have escaped the attacks of their 

 enemies and thus become adapted to a new medium. Of 

 fixed, creeping, and swimming forms of animal life there are 



