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absence acter adaptation American animals appear bees bird blastomere breeder breeding cells cent characters chromosomes color corn crinoids cross Darwin determined dk.br dominant ecologist ecology eggs environment evidence evolution experiment experimental fact factors female fertilization flowers forms genus green growth gynandromorphs hair Heredity heterozygote hybrids important index number individuals inheritance insects kelps lamina large number larva Lessoniopsis lt.br male matter measurements Mendelian Mendelian inheritance methods mice morphology muscular articulations mutation natural selection Notes and Literature observed organs Origin of Species orthogenesis oyster pairs paper Paramecium parent pinnule plants present problem produced Professor pure race Raymond Pearl rays Recapitulation Theory recent region relation Science seed seems selection index Shorter Articles single soil specimens sporophytic stipe structure syzygy T. H. Morgan temperature theory tion toads variability variations varieties vascular vegetation Vries xerophytic yellow
Page 82 - But as my conclusions have lately been much misrepresented, 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 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 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 385 - ... 1 Papers from the Biological Laboratory of the Maine Agricultural Experiment Station. No.
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.
Page 81 - There are, however, some who still think that species have suddenly given birth, through quite unexplained means, to new and totally different forms: but, as I have attempted to show, weighty evidence can be opposed to the admission of great and abrupt modifications. Under a scientific point of view, and as leading to further investigation, but little advantage is gained by believing that new forms are suddenly developed in an inexplicable manner from old and widely different forms, over the old...