The Origin of Species by Means of Natural Selection,: Or the Preservation of Favoured Races in the Struggle for LifeJohn Murray, Albemarle Street., 1891 - 432페이지 |
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viii 페이지
... occasional means - Dispersal during the Glacial period - Alternate Glacial periods in the north and south 296 CHAPTER XIII . GEOGRAPHICAL DISTRIBUTION - Continued . Distribution of fresh - water productions - On the inhabitants of ...
... occasional means - Dispersal during the Glacial period - Alternate Glacial periods in the north and south 296 CHAPTER XIII . GEOGRAPHICAL DISTRIBUTION - Continued . Distribution of fresh - water productions - On the inhabitants of ...
10 페이지
... a single variety should have been turned loose in its new home . Nevertheless , as our varieties certainly do occasionally revert in some of their characters to ancestral forms , it seems. 10 VARIATION UNDER DOMESTICATION . [ CHAP . I.
... a single variety should have been turned loose in its new home . Nevertheless , as our varieties certainly do occasionally revert in some of their characters to ancestral forms , it seems. 10 VARIATION UNDER DOMESTICATION . [ CHAP . I.
14 페이지
... occasional crosses , if aided by the care- ful selection of the individuals which present the desired character ; but to obtain a race intermediate between two quite distinct races , would be very difficult . Sir J. Sebright expressly ...
... occasional crosses , if aided by the care- ful selection of the individuals which present the desired character ; but to obtain a race intermediate between two quite distinct races , would be very difficult . Sir J. Sebright expressly ...
19 페이지
... occasional re - appearance of the blue colour and various black marks in all the breeds , both when kept pure and when crossed ; -and lastly , the mongrel off- spring being perfectly fertile ; -from these several reasons , taken ...
... occasional re - appearance of the blue colour and various black marks in all the breeds , both when kept pure and when crossed ; -and lastly , the mongrel off- spring being perfectly fertile ; -from these several reasons , taken ...
25 페이지
... occasional preservation of the best individuals , whether or not sufficiently distinct to be ranked at their first appearance as dis- tinct varieties , and whether or not two or more species or races have become blended together by ...
... occasional preservation of the best individuals , whether or not sufficiently distinct to be ranked at their first appearance as dis- tinct varieties , and whether or not two or more species or races have become blended together by ...
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accumulated adapted admit affinities allied species America analogous ancient appear beak become bees believe belonging birds breeds cause cells characters climate closely allied colour continued crossed crustaceans degree developed difficulty distinct species domestic animals doubt effects eggs embryo existing extinct extremely facts favourable female fertilised fertility flowers formation formerly forms fossil Fritz Müller genera genus geological geological period Glacial period gradations greater number habits Hence hybrids important increase individuals inhabitants inherited insects instance instincts intercrossing intermediate kind lamellæ larvæ less living male mammals manner Marsupials migration modified descendants natural selection naturalists nearly nest occasionally occur oceanic islands offspring organisation organs parent peculiar perfect pigeon pistil pollen present preserved principle probably produced quadrupeds ranked reciprocal crosses remarked resemblance rudimentary seeds sexual selection Silurian slight South America stamens sterility structure successive supposed tend theory tion variability variations varieties vary whilst whole wings young