Great Books of the Western World: DarwinRobert Maynard Hutchins W. Benton, 1952 For contents, see Title Catalog. |
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Стр. 31
... varieties or incipient species greater than the average are now manufacturing , many of the species already manufactured still to a certain extent resemble varieties , for they differ from each other by less than the usual amount of ...
... varieties or incipient species greater than the average are now manufacturing , many of the species already manufactured still to a certain extent resemble varieties , for they differ from each other by less than the usual amount of ...
Стр. 148
... varieties have not been produced which are mutually sterile ; and why with plants only a few such cases , immediately to be given , have been observed . The real difficulty in our present subject is not , as it appears to me , why ...
... varieties have not been produced which are mutually sterile ; and why with plants only a few such cases , immediately to be given , have been observed . The real difficulty in our present subject is not , as it appears to me , why ...
Стр. 149
... varieties , when used either as the father or mother , and crossed with the Nicotiana glutinosa , always yielded hybrids not so sterile as those which were produced from the four other varieties when crossed with N. glutinosa . Hence ...
... varieties , when used either as the father or mother , and crossed with the Nicotiana glutinosa , always yielded hybrids not so sterile as those which were produced from the four other varieties when crossed with N. glutinosa . Hence ...
Содержание
THE ORIGIN OF SPECIES Page | 1 |
Causes of variability Effects of habit and the use or tures variable Parts developed in an unusual manner are highly variable specific characters more ... | 12 |
Variability Individual differences Doubtful species tion Cases of difficulty Natura non facit saltum Organs of small importance Organs not in all cases | 29 |
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adapted affinities America ancient appear beak become bees believe belonging birds breeds cause cells characters cies climate closely allied colour common continent crossed crustaceans degree developed difficulty distinct species doubt eggs embryo existing extinct extremely fact favourable female fertilised fertility flowers formation forms fossil Fritz Müller Gärtner genera genus geological geological period gradations greater number habits Hence hybrids hybrids produced important individuals inhabitants inherited insects instance instincts intercrossing intermediate intervals kind lamellæ larvæ less living male mammæ mammals manner marsupials migration modified descendants natural selection naturalists nearly nest occur offspring organisation organs parent peculiar perfect pigeon pistil pollen present principle probably produced progenitor quadrupeds races ranked reciprocal crosses relation remarked resemblance rudimentary seeds sexual sexual selection slight South America stamens sterility structure supposed tend theory tion variability variations varieties vary whilst whole widely wings young