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
... insects- Summary 189 CHAPTER VIII HYBRIDISM Distinction between the sterility of first crosses and of hybrids - Sterility various in degree , not universal , affected by close inter- breeding , removed by domestication - Laws governing ...
... insects- Summary 189 CHAPTER VIII HYBRIDISM Distinction between the sterility of first crosses and of hybrids - Sterility various in degree , not universal , affected by close inter- breeding , removed by domestication - Laws governing ...
15 페이지
... insects under the bark of trees . In the case of the mistletoe , which draws its nourishment from certain trees , which has seeds that must be transported by certain birds , and which has flowers with separate sexes absolutely re ...
... insects under the bark of trees . In the case of the mistletoe , which draws its nourishment from certain trees , which has seeds that must be transported by certain birds , and which has flowers with separate sexes absolutely re ...
51 페이지
... insects are very far from uniform . [ Authors sometimes argue in a circle when they state that important organs never vary ; for these same authors practically rank that character as important ( as some few naturalists have honestly ...
... insects are very far from uniform . [ Authors sometimes argue in a circle when they state that important organs never vary ; for these same authors practically rank that character as important ( as some few naturalists have honestly ...
53 페이지
... insects in North America and Europe , which differ very slightly from each other , have been ranked by one eminent naturalist as undoubted species , and by another as varieties , or , as they are often called , as geographical races ...
... insects in North America and Europe , which differ very slightly from each other , have been ranked by one eminent naturalist as undoubted species , and by another as varieties , or , as they are often called , as geographical races ...
59 페이지
... insects of two districts , into two nearly equal masses , the species of the larger genera on one side , and those of the smaller genera on the other side , and it has invariably proved to be the case that a larger proportion of the ...
... insects of two districts , into two nearly equal masses , the species of the larger genera on one side , and those of the smaller genera on the other side , and it has invariably proved to be the case that a larger proportion of the ...
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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