Evolution and animal life, an elementary discussion of facts, processes, laws and theories relating to the life and evolution of animalsD. Appleton, 1908 - Всего страниц: 489 |
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Стр. 51
... females have chosen for their consorts those males best endowed by variation with these ornamental character- istics , so that by this selection there has come about a gradual cumulation of the characteristics culminating in such ...
... females have chosen for their consorts those males best endowed by variation with these ornamental character- istics , so that by this selection there has come about a gradual cumulation of the characteristics culminating in such ...
Стр. 52
... female or hermaphroditic plant or animal produces , at least in the condition of eggs or germ cells , more than one new individual like itself . ( There are a very few exceptional cases , compensated for , however , in other ways ...
... female or hermaphroditic plant or animal produces , at least in the condition of eggs or germ cells , more than one new individual like itself . ( There are a very few exceptional cases , compensated for , however , in other ways ...
Стр. 59
... female quinnat salmon of the Columbia , Oncorhynchus tchawytscha , ascends the river at the age of about four years , and lays 4,000 eggs , after which she dies . Half these eggs develop into males . If each female egg came to maturity ...
... female quinnat salmon of the Columbia , Oncorhynchus tchawytscha , ascends the river at the age of about four years , and lays 4,000 eggs , after which she dies . Half these eggs develop into males . If each female egg came to maturity ...
Стр. 71
... female individuals of the same species are the rule rather than the exception ( Fig . 40 ) . Many of these differences are what might be called the necessary ones due to the particular functions assumed by each individual in this ...
... female individuals of the same species are the rule rather than the exception ( Fig . 40 ) . Many of these differences are what might be called the necessary ones due to the particular functions assumed by each individual in this ...
Стр. 72
... female mammals , the brood pouches of the female kangaroos and opossums , etc. But a moment's reflection calls to mind the existence of a host of other differ- ences between males and females of the same species which plainly have no ...
... female mammals , the brood pouches of the female kangaroos and opossums , etc. But a moment's reflection calls to mind the existence of a host of other differ- ences between males and females of the same species which plainly have no ...
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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