The Origin of Species, Том 2Books, Incorporated, 1900 - Всего страниц: 365 |
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Стр. 246
... difficulty of making a first cross , and the sterility of the hybrids thus produced - two classes of facts which are generally confounded together - is by no means strict . There are many cases , in which two pure species , as in the ...
... difficulty of making a first cross , and the sterility of the hybrids thus produced - two classes of facts which are generally confounded together - is by no means strict . There are many cases , in which two pure species , as in the ...
Стр. 250
... difficulty , on the gooseberry . We have seen that the sterility of hybrids which have their re- productive organs in an imperfect condition , is a different case from the difficulty of uniting two pure species which have their ...
... difficulty , on the gooseberry . We have seen that the sterility of hybrids which have their re- productive organs in an imperfect condition , is a different case from the difficulty of uniting two pure species which have their ...
Стр. 327
... difficulty in believing that they have migrated from the same region ; for during the vast geographical and climatical changes which have supervened since ancient times , almost any amount of migration is possible . But in many other ...
... difficulty in believing that they have migrated from the same region ; for during the vast geographical and climatical changes which have supervened since ancient times , almost any amount of migration is possible . But in many other ...
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Часто встречающиеся слова и выражения
adapted admit affinity ancient animals appear Archipelago areas become believe belonging birds Cambrian characters classification climate closely allied species common continent creation crustaceans degree deposits descent with modification developed difficulty distant distinct species domestic doubt embryo Europe existing extinct facts faunas fertility flowers formations formerly forms fossil fresh-water Fritz Müller Gärtner genera genus geological period geological record Glacial period groups of species habits hybrids hybrids produced important INDIANENSIS individuals inhabitants inherited insects instance intermediate intervals land larvæ less living mammæ mammals manner marine Marsupials MDCCCXX migration modified descendants mongrels mountains natural selection naturalists nearly oceanic islands offspring parent peculiar perfect pistil plants pollen present probably produced progenitor quadrupeds reciprocal crosses regions remains remarked reproductive resemblance rocks rudimentary organs seeds SIGILLUM Silurian South America stage stamens sterility structure successive suppose terrestrial tertiary theory of natural tion variations varieties VERITAS whole widely different