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POPULAR SCIENCE MONTHLY 



guinea-pigs, one can obtain within two generations any desired com- 

 bination of the three pairs of alternative coat-characters, if one pro- 



F:g. 12. A Long-haired, Rough, Pigmented Guinea-pig. 



Fig 13. An Imperfectly Long-haiked Guinea-pig. Compare Figs. 4, 7 and 12. 



duces a sufficiently large number of individuals; but to obtain the 

 desired combination in individuals which will breed true is not so 

 simple a matter. If the desired combination consists wholly of reces- 



