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absence adaptation American animals appear become bees body breeding called cause cells cent characters close color conclusion continued corn course cross Darwin described determined direct discussion dk.br effect eggs environment evidence evolution exist experiments fact factors flowers forms further gametophytes give given green growing growth hair heredity idea important increase indicate individuals inheritance insects interesting kind known leaves less light male matter means measurements methods mutation natural Notes observed occur organs origin parent plants Pleistocene possible present probably problem produced Professor pure question race reason recent reference regard region relation represented says Science seems selection side similar single species specimens stages structure theory tion true unit variability variations varieties visits whole yellow
Page 170 - This has been effected chiefly through the natural selection of numerous successive, slight, favourable variations ; aided in an important manner by the inherited effects of the use and disuse of parts ; and in an unimportant manner, that is in relation to adaptive structures, whether past or present, by the direct action of external conditions, and by variations which seem to us in our ignorance to arise spontaneously.
Page 73 - No man would ever try to make a fantail till he saw a pigeon with a tail developed in some slight degree in an unusual manner, or a pouter...
Page 145 - We are thus brought to the question which has been largely discussed by naturalists, namely, whether species have been created at one or more points of the earth's surface. Undoubtedly there are very many cases of extreme difficulty, in understanding how the same species could possibly have migrated from some one point to the several distant and isolated points, where now found. Nevertheless the simplicity of the view that each species was first produced within a single region captivates the...
Page 85 - Our ignorance of the laws of variation is profound. Not in one case out of a hundred can we pretend to assign any reason why this or that part differs, more or less, from the same part in the parents.
Page 385 - ... 1 Papers from the Biological Laboratory of the Maine Agricultural Experiment Station. No.
Page 170 - ... and it has been stated that I attribute the modification of species exclusively to natural selection, I may be permitted to remark that in the first edition of this work, and subsequently, I placed in a most conspicuous position— namely, at the close of the Introduction — the following words: "I am convinced that natural selection has been the main but not the exclusive means of modification.
Page 83 - One of the most remarkable features in our domesticated races is that we see in them adaptation, not indeed to 'the animal's or plant's own good, but to man's use or fancy.
Page 151 - The direct action of changed conditions leads to definite or indefinite results. In the latter case the organisation seems to become plastic, and we have much fluctuating variability. In the former case the nature of the organism is such that it yields readily, when subjected to certain conditions, and all, or nearly all the individuals become modified in the same way.
Page 148 - ... to natural selection, by affording a better chance of the occurrence of profitable variations. Unless such occur, natural selection can do nothing. Under the term of " variations," it must never be forgotten that mere individual differences are included.