On the Origin of Species by Means of Natural Selection: Or, The Preservation of Favoured Races in the Struggle for LifeD. Appleton, 1909 - 430페이지 |
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15 페이지
... birds , and which has flowers with separate sexes absolutely re- quiring the agency of certain insects to bring pollen from one flower to the other , it is equally preposterous to account for the structure of this parasite , with its ...
... birds , and which has flowers with separate sexes absolutely re- quiring the agency of certain insects to bring pollen from one flower to the other , it is equally preposterous to account for the structure of this parasite , with its ...
20 페이지
... birds , with the rarest exceptions , hardly ever lay fertile eggs . Many exotic plants have pollen utterly worthless , in the same exact condition as in the most sterile hybrids . When , on the one hand , we see domesticated animals and ...
... birds , with the rarest exceptions , hardly ever lay fertile eggs . Many exotic plants have pollen utterly worthless , in the same exact condition as in the most sterile hybrids . When , on the one hand , we see domesticated animals and ...
30 페이지
... bird , is also remark- able from the wonderful development of the caruncu- lated skin about the head ; and this is ... birds the head and tail touch : the oil - gland is quite 3 aborted . Several other less distinct breeds might be ...
... bird , is also remark- able from the wonderful development of the caruncu- lated skin about the head ; and this is ... birds the head and tail touch : the oil - gland is quite 3 aborted . Several other less distinct breeds might be ...
31 페이지
... birds are clothed when hatched . The shape and size of the eggs vary . The manner of flight , and in some breeds the voice and disposition , differ re- márkably . Lastly , in certain breeds , the males and females have come to differ to ...
... birds are clothed when hatched . The shape and size of the eggs vary . The manner of flight , and in some breeds the voice and disposition , differ re- márkably . Lastly , in certain breeds , the males and females have come to differ to ...
32 페이지
... birds breeding on preci- pices , and good fliers , are unlikely to be exterminated ; and the common rock - pigeon , which has the same habits with the domestic breeds , has not been exterminated even on several of the smaller British ...
... birds breeding on preci- pices , and good fliers , are unlikely to be exterminated ; and the common rock - pigeon , which has the same habits with the domestic breeds , has not been exterminated even on several of the smaller British ...
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accumulated adapted affinities allied species America analogous ancient animals appear archipelago become bees believe birds breeds cause cells characters cirripedes climate closely allied colour continuous crossed crustaceans degree difficulty distinct species divergence domestic doubt embryo endemic existing exterminated extinct extremely facts favourable fertilised fertility flowers formations forms fossil Gärtner genera genus geological geological period Glacial period gradations greater number groups of species habits Hence hybrids hybrids produced important increase individuals inhabitants inherited insects instance instincts intercrossing intermediate larvæ laws less living males mammals manner migration modification modified descendants natural selection naturalists nearly nest occasionally offspring organic organisation origin of species perfect pigeons plants pollen present principle probably produced progenitor ranked reciprocal crosses remarked resemble rock-pigeon rudimentary seeds sexual sexual selection Silurian slight sometimes South America sterility structure struggle successive supposed swimbladder tend theory variability variations varieties vary whole widely