CHAPTER XLVI 



ANIMAL BREEDING 



Questions. 1. How can animals be made to lose qualities or to take 

 on new ones ? 2. Are the results of training passed on to the next genera- 

 tion ? 3. If dogs' tails were cut off each generation, would the breed 

 finally lose the tail ? 4. Are acquired characters inherited ? 5. Can all 

 kinds of animals be domesticated ? 6. Can two animals of different spe- 

 cies produce offspring? 7. Are all hybrids sterile Hke the mule? 8. What 

 is there to show that modern varieties are really different from their 

 ancestors ? 9. Do animals in a state of nature become changed the way 

 domestic animals do ? 



378. Domestic animals. We have no exact history of the be- 

 ginnings of man's domestication of animals, but indirectly we 

 can tell that this relationship has extended over many thousands 

 of years. The total number of species is really not very great ; 

 the remarkable thing is the tremendous amount of variation 

 within each species. Anyone who has ever attended a dog show 

 or a poultry show, for example, cannot help wondering where 

 all the varieties came from and how they were produced. 



With very few exceptions all the domesticated animals are 

 vertebrates, chiefly mammals and a few birds. The dog, the 

 horse, the ox, the sheep, and the pig represent the principal 

 groups of domesticated animals. The cat has been at home in 

 our dwellings for at least three thousand years, but it does not 

 approach the others in importance, either as a companion or as 

 a serviceable animal. The camel and the elephant have been 

 domesticated in Africa and Asia. Many other animals have 

 been cultivated as pets, such as rabbits, mice, guinea pigs, and 

 even skunks, woodchucks, and squirrels. In recent years at- 

 tempts have been made to develop farms for fur-bearing animals 

 such as the silver fox and the muskrat, and these have met 



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