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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9 페이지
... crossing - Fertility of varieties when crossed and of their mongrel offspring not universal - Hybrids and mongrels compared independently of their fertility - Summary 219 CHAPTER IX ON THE IMPERFECTION OF THE GEOLOGICAL RECORD On the ...
... crossing - Fertility of varieties when crossed and of their mongrel offspring not universal - Hybrids and mongrels compared independently of their fertility - Summary 219 CHAPTER IX ON THE IMPERFECTION OF THE GEOLOGICAL RECORD On the ...
26 페이지
... crossed , -a subject hereafter to be discussed ) , domestic races of the same species differ from each other in the same manner as , only in most cases in a lesser degree than , do closely - allied species of the same genus in a state ...
... crossed , -a subject hereafter to be discussed ) , domestic races of the same species differ from each other in the same manner as , only in most cases in a lesser degree than , do closely - allied species of the same genus in a state ...
29 페이지
... crossing of a few aboriginal species ; but by crossing we can only get forms in some degree intermediate between their parents ... crossed one with another for several generations , hardly two of them will be alike ; and then the extreme ...
... crossing of a few aboriginal species ; but by crossing we can only get forms in some degree intermediate between their parents ... crossed one with another for several generations , hardly two of them will be alike ; and then the extreme ...
32 페이지
... crossing of any lesser number ; how , for instance , could a pouter be produced by crossing two breeds unless one of the parent - stocks possessed the characteristic enormous crop ? The supposed aboriginal stocks must all have been rock ...
... crossing of any lesser number ; how , for instance , could a pouter be produced by crossing two breeds unless one of the parent - stocks possessed the characteristic enormous crop ? The supposed aboriginal stocks must all have been rock ...
33 페이지
... crossed a barb with a spot , which is a white bird with a red tail and red spot on the forehead , and which notoriously breeds very true ; the mongrels were dusky and mottled . I then crossed one of the mongrel barb - fantails with a ...
... crossed a barb with a spot , which is a white bird with a red tail and red spot on the forehead , and which notoriously breeds very true ; the mongrels were dusky and mottled . I then crossed one of the mongrel barb - fantails with a ...
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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