guinea-pigs, one can obtain within two generations any desired combination of the three pairs of alternative coat-characters, if one produces

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

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

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-