Animal Life: A First Book of ZoölogyD. Appleton, 1900 - Всего страниц: 329 |
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Стр. 8
... grows . But there seem to be some fixed limits to the extent of this increase in size . No Amaba becomes large . A remarkable phenomenon always occurs to prevent this . An Amaba which has grown for some time contracts all. ANIMAL LIFE.
... grows . But there seem to be some fixed limits to the extent of this increase in size . No Amaba becomes large . A remarkable phenomenon always occurs to prevent this . An Amaba which has grown for some time contracts all. ANIMAL LIFE.
Стр. 9
... grow , and reproduce by fission . It is very evident that this is so , for any part of the body or the whole body was ... grows , and finally divides in two . 5. Paramecium . - Another protozoan which is common in stagnant pools and can ...
... grow , and reproduce by fission . It is very evident that this is so , for any part of the body or the whole body was ... grows , and finally divides in two . 5. Paramecium . - Another protozoan which is common in stagnant pools and can ...
Стр. 11
... grow larger , in order to be exactly like their parent . The new Paramacia attain full size and then divide , each into two . And so on for many generations . But it has been discovered that this simplest kind of reproduction can not go ...
... grow larger , in order to be exactly like their parent . The new Paramacia attain full size and then divide , each into two . And so on for many generations . But it has been discovered that this simplest kind of reproduction can not go ...
Стр. 15
... grow and develop into a new Gre- garina . In some species there are fine ducts or canals leading from the center of the cyst through the wall to the outside , and through these canals the spores issue . Some- times two Gregarinæ come ...
... grow and develop into a new Gre- garina . In some species there are fine ducts or canals leading from the center of the cyst through the wall to the outside , and through these canals the spores issue . Some- times two Gregarinæ come ...
Стр. 26
... grows to the size of the original colony . This kind of multiplication or reproduction may be continued for several generations . But it does not go on indefinitely . After a number of these gener- ations has been produced by simple ...
... grows to the size of the original colony . This kind of multiplication or reproduction may be continued for several generations . But it does not go on indefinitely . After a number of these gener- ations has been produced by simple ...
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adaptation adult alimentary canal Amaba ants artificial selection becomes bees beetles birds body wall breathing butterfly called cavity chitin CLASS colony color complex animals composed conjugation crab differentiation digestion divide division of labor ectoderm egg cells embryo existence feed female fertilized fish flagella free-swimming function gastrula Globigerinæ habits hatched higher animals honey-bee Hydra inclosed increase insects instinct intestine jelly-fishes kinds of animals larva larvæ layer live male mals mammals many-celled animals mass medusæ metamorphosis naturalists nerve nest nucleus ocean one-celled organs outer oxygen Pandorina papillæ Paramecium parasites parent perform plant-lice plants polyp prey primitive processes produced protoplasm Protozoa pseudopods pupa queen Radiolaria reproductive cells Sacculina sea-anemone shell simple simplest animals single cell special sense species sperm cells spherical sponge stage structure substance surface swimming tentacles tion tissues vertebrates Volvox Vorticella wings workers worms young
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Стр. 115 - There is no exception to the rule that every organic being naturally increases at so high a rate, that, if not destroyed, the earth would soon be covered by the progeny of a single pair. Even slow-breeding man has doubled in twenty-five years, and at this rate, in less than a thousand years, there would literally not be standing room for his progeny.
Стр. 215 - He cannot be mistaken for any other, and his flaming vest and blue stockings show that he does not court concealment. He is very abundant in the damp woods, and I was convinced he was uneatable so soon as I made his acquaintance and saw the happy sense of security with which he hopped about. I took a few specimens home with me, and tried my fowls and ducks with them ; but none would touch them. At last, by throwing down pieces of meat, for which there was a great competition amongst them, I managed...
Стр. 20 - ... inhabitants of the water has followed a roundabout path from the surface to the bottom and then back into the water. When this fact is seen in all its bearings and its full significance is grasped, it is certainly one of the most notable and instructive features of evolution. The food-supply of marine animals consists of a few species of microscopic organisms which are inexhaustible and the only source of food for all the inhabitants of the ocean.
Стр. 116 - The elephant is reckoned the slowest breeder of all known animals, and I have taken some pains to estimate its probable minimum rate of natural increase; it will be safest to assume that it begins breeding when thirty years old, and goes on breeding till ninety years old, bringing forth six young in the interval, and surviving till one hundred years old ; if this be so, after a period of from 740 to 750 years there would be nearly nineteen million elephants alive, descended from the first pair.