The American Naturalist, Volume 43Essex Institute, 1909 - Biology |
From inside the book
Results 1-5 of 100
Page 55
... variations and aberrations among insects . However , there is , as yet , little proof that they produce heritable modifications such as we believe real species to be made of . In this regard Tower's work with Leptinotarsa is a ...
... variations and aberrations among insects . However , there is , as yet , little proof that they produce heritable modifications such as we believe real species to be made of . In this regard Tower's work with Leptinotarsa is a ...
Page 56
... variation in Amblystoma tigrinum and promises proof that cer- tain of these are inherited or at least perpetuated by ... variations in the appetite are inherited , we should have an interesting case of indirect transmission of characters ...
... variation in Amblystoma tigrinum and promises proof that cer- tain of these are inherited or at least perpetuated by ... variations in the appetite are inherited , we should have an interesting case of indirect transmission of characters ...
Page 58
... variations in size , which , in one case , were 1.8 mm . , 1.2 mm . , 1.15 mm . , and 1.05 mm . in diameter . The eggs measuring 1.15-1.20 mm . were most abundant . Contrary to what one might expect , there is no relation be- tween the ...
... variations in size , which , in one case , were 1.8 mm . , 1.2 mm . , 1.15 mm . , and 1.05 mm . in diameter . The eggs measuring 1.15-1.20 mm . were most abundant . Contrary to what one might expect , there is no relation be- tween the ...
Page 60
... variations in size of the eggs may of course be also true in case of the sperms , which might thus be a factor determining the size of the young . At any rate , Chambers made an interesting observation that tadpoles developed from eggs ...
... variations in size of the eggs may of course be also true in case of the sperms , which might thus be a factor determining the size of the young . At any rate , Chambers made an interesting observation that tadpoles developed from eggs ...
Page 67
... variations that occur in the constitutions or characters of organisms some must happen to be in directions to give ... variations never ex- certain narrow boundaries built round species like inviolable walls . Curiously enough , Darwin ...
... variations that occur in the constitutions or characters of organisms some must happen to be in directions to give ... variations never ex- certain narrow boundaries built round species like inviolable walls . Curiously enough , Darwin ...
Other editions - View all
Common terms and phrases
absence adaptation American animals appear bees breeding brown cells cent chromosomes corn plant correlation crinoids crossed curve Darwin dk.br dominant ecology eggs elementary species environment evidence evolution experimental experiments fact factors fertilization flowers fluctuating forms gametes genus green growth gynandromorphs hair color heredity heterozygote hybrids important index number individuals inheritance insects kelps L. H. BAILEY lamina large number larva larvæ Lessoniopsis lt.br male Mendelian Mendelian inheritance methods morphology muscular articulations mutation natural selection Notes and Literature observed offspring organs origin Origin of Species oyster pairs pangen paper Paramecium parent physiological pigment pinnule present problem produced Professor pure race RAYMOND PEARL rays Recapitulation Theory recent region relation Science seems selection index single sired specimens sporophytic stipe structure T. H. MORGAN theory tion unit characters variability variations varieties vegetation Vries yellow
Popular passages
Page 78 - 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 156 - If numerous species, belonging to the same genera or families, have really started into life at once, the fact would be fatal to the theory of evolution through natural selection.
Page 69 - 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 135 - 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 81 - 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 79 - 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 377 - ... 1 Papers from the Biological Laboratory of the Maine Agricultural Experiment Station. No.
Page 141 - 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 138 - ... 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 77 - 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...