TUE MOUSE 427 



Among insects bees have been domesticated from early 

 times. The hal)its of the tame bees differ httle from those in 

 the wild state. In place of a hollow tree a box is provided 

 which is so arranged that an excess of honey may be withdrawn 

 without jeopardizing the life of the colony. The different races 

 of domesticated bees differ much in color and in amiability. 

 Perhaps of greater economic importance than bees are the silk 

 moths, which manufacture silk threads in the construction of 

 their cocoons. By proper treatment in hot water the threads 

 are unwound from the cocoon. A number of these fine threads 

 are spun together into stouter threads suitable for use in the 

 manufacture of silk cloths. 



This review of domestic animals shows that species that are 

 under the care of man are much more variable than wild species. 

 Why is this? Because man controls the breeding of domesti- 

 cated animals. He carefully observes the j'oung produced 

 each year, and selects those that best conform to his ideal, or 

 which possess some striking peculiarity which may be of eco- 

 nomic importance. Any such peculiarity of an individual will 

 be transmitted to its offspring. Thus a race may l^e improved 

 or a new one founded. In the formation of perfected races, 

 two processes are involved. First, an individual must appear 

 with .some new, some peculiar characteristic. Second, there 

 must be a selection, a preservation, of the most perfect de- 

 scendants of this individual. Bj^ such means the race is im- 

 proved. Charles Darwin,' to whom is due the present accept- 

 ance by naturalists of the theory of evolution, came to the 

 conclusion that nature works vnih species in the same way that 

 man does. Of the vast number of individuals produced in 

 each generation in the wild state only a few survive, and these, 



< Fig. 392. 



