Evolution and animal life, an elementary discussion of facts, processes, laws and theories relating to the life and evolution of animalsD. Appleton, 1907 - Всего страниц: 489 |
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Стр. ix
... cells , 217 ; Simplest many- celled animals , 218 ; Effects of sex , 220 ; Sex dimorphism , 221 ; The life cycle ... Cell division , 251 ; Mitosis , or karyokinesis , 252 ; Somatic and germ tissues , 257 ; Reproduction in protozoa , 260 ...
... cells , 217 ; Simplest many- celled animals , 218 ; Effects of sex , 220 ; Sex dimorphism , 221 ; The life cycle ... Cell division , 251 ; Mitosis , or karyokinesis , 252 ; Somatic and germ tissues , 257 ; Reproduction in protozoa , 260 ...
Стр. 3
... germ or egg . Each egg cell by segmentation divides into two daughter cells , and these , through the influence of ... germ cell itself , and its existence as the " physical basis of heredity " is now well established . In a later ...
... germ or egg . Each egg cell by segmentation divides into two daughter cells , and these , through the influence of ... germ cell itself , and its existence as the " physical basis of heredity " is now well established . In a later ...
Стр. 19
... germ cells of the same parent are ever quite alike . No two cells in the body are ever exactly identical . Among plants of the same kind in the field , some are cut down by frost while others persist ; some are destroyed by drought ...
... germ cells of the same parent are ever quite alike . No two cells in the body are ever exactly identical . Among plants of the same kind in the field , some are cut down by frost while others persist ; some are destroyed by drought ...
Стр. 21
... cells are absolutely alike , and in the variance of the germ cells , from which individuals spring , all the elements of their future variation are involved . Without further discussion , it is evident that variety in life . is a factor ...
... cells are absolutely alike , and in the variance of the germ cells , from which individuals spring , all the elements of their future variation are involved . Without further discussion , it is evident that variety in life . is a factor ...
Стр. 52
... germ cells , more than one new individual like itself . ( There are a very few exceptional cases , compensated for , however , in other ways . ) Most produce many new individuals and some reproduce enormously . Cer- tain fishes lay ...
... germ cells , more than one new individual like itself . ( There are a very few exceptional cases , compensated for , however , in other ways . ) Most produce many new individuals and some reproduce enormously . Cer- tain fishes lay ...
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actual adaptation adult animals animals and plants ants apes appear artificial selection bees beetles biologists birds body breeding butterfly called causes centrosome changes CHAPTER characters chromatin chromosomes color and pattern common crab Darwin degeneration degree descent differentiation division egg cell embryo environment existence fact factors fauna female fertilized fishes forms fossils genus germ cells habit hatched heredity honeybee host hybrid individuals influence inheritance insects instinct islands isolation kinds of animals known larva larvæ live lower male mammals matter ment modified mutations natural selection naturalists nest nucleus offspring organic evolution origin Origin of Species parasites parent phenomena plasm primitive produced protoplasm Protozoa race relation reproduction reptiles resemblance Sacculina sea anemone sexual sexual selection sheep species species-forming sperm spines stage structure substance tail theory tion traits tree variation various vertebrates Weismann wings workers young
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Стр. 468 - There is grandeur in this view of life, with its several powers, having been originally breathed by the Creator into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being evolved.
Стр. 426 - ... the plain duty of each and all of us is to try to make the little corner he can influence somewhat less miserable and somewhat less ignorant than it was before he entered it. To do this effectually it is necessary to be fully possessed of two beliefs — the first, that the order of nature is ascertainable by our faculties to an extent which is practically unlimited; the second, that our volition counts for something as a condition of the course of events.
Стр. 426 - We live in a world which is full of misery and ignorance, and the plain duty of each and all of us is to try to make the little corner he can influence somewhat less miserable and somewhat less ignorant than it was before he entered it.
Стр. 137 - 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.
Стр. 468 - To my mind it accords better with what we know of the laws impressed on matter by the Creator, that the production and extinction of the past and present inhabitants of the world should have been due to secondary causes, like those determining the birth and death of the individual.
Стр. 120 - Given any species in any region, the nearest related species is not likely to be found in the same region nor in a remote region, but in a neighboring district separated from the first by a barrier of some sort, or at least by a belt of country, the breadth of which gives the effect of a barrier.
Стр. 63 - Near villages and small towns I have found the nests of humble-bees more numerous than elsewhere, which I attribute to the number of cats that destroy the mice." Hence it is quite credible that the presence of a feline animal in large numbers in a district might determine, through the intervention first of mice and then of bees, the frequency of certain flowers in that district!
Стр. 311 - There are twenty-six land birds. Of these twenty-one, or perhaps twenty-three, are ranked as distinct species, and would commonly be assumed to have been here created; yet the close affinity of most of these birds to American species is manifest in every character in their habits, gestures and tones of voice.
Стр. 63 - Newman, who has long attended to the habits of humble-bees, believes that "more than two-thirds of them are thus destroyed all over England.