The Origin of Species —— By Means of Natural Selection, or the Preservation of Favored Races in the Struggle for Life

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ISBN: 9781330018934 出版年：2016 页码：345 Charles Darwin Forgotten Books

Distinction between the sterility of first crosses and of hybrids Sterility various in degree, not universal, affected by close in terbreeding, removed by domestication — Laws governing the sterility of hybrids — Sterility not a special endowment, but incidental on other difierences, not accumulated by natural selection — Causes of the sterility of first crosses and of hybrids — Parallelism between the effects of changed conditions of life and of crossing — Dimorphism and trimorphism — Fertility of varieties when crossed and of their mongrel ofispring not uni versal — Hybrids and mongrels compared independently of their fertility — Summary.