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weakest

die.

☆、正文 9 HYBRIDISM.（1）

Distinction

between

the

sterility

of first

crosses

and of

hybrids.

Sterility

various in

degree,

not

universal,

affected

by close

inter-

breeding,

removed by

domestication.

Laws

governing

the

sterility

of

hybrids.

Sterility

not a

special

endowment,

but

incidental

on other

differences.

Causes of

the

sterility

of first

crosses

and of hy-

brids.

Parallelism

between

the

effects of

changed

conditions

of life