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active adapted adult alimentary canal animals ants appearance attached bear become bees birds blood body called carried cells certain changes character close color common complete consists continually covered crabs digestive eggs enemies example exist extend external eyes fact feed feet female finally fishes forms gills give greater grow habits hand hatched head highly individuals insects instinct kinds known larger leaves legs length less live lower male mammals matter means mouth natural nerve nest occur organs pair parasites parent pass plants portion possess present produced protection regions relatively remains reptiles resemblance result rocks scale seen sense serve shell side similar simple skin species stage structure substance surface surroundings swimming tail teeth tion tree United usually various wall wings workers worms young
Página 282 - 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.
Página 264 - Fig. 41 are indistinguishably alike, but one embryo is sure to develop into a fish and the other into a salamander. This certainty of an embryo to become an individual of a certain kind is called the law of heredity.
Página 343 - Tremex burrow is reached she deposits an egg in it. The larva that hatches from this egg creeps along this burrow until it reaches its victim, and then fastens itself to the horntail larva, which it destroys by sucking its blood. The larva of...
Página 362 - 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...
Página 329 - Steppes, he once saw an eagle belonging to an altogether gregarious species (the white-tailed eagle, jfaliaetos albicilla) rising high in the air ; for half an hour it was describing its wide circles in silence when at once its piercing voice was heard. Its cry was soon answered by another eagle which approached it, and was followed by a third, a fourth, and so on, till nine or ten eagles came together and soon disappeared.
Página 283 - 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.
Página 363 - There are two intensely black spots on this margin in the appropriate position for eyes, and the whole appearance is that of a large flat face extending to the outer edge of the red margin. The effect is an intensely exaggerated caricature of a vertebrate face, which is probably alarming to the vertebrate enemies of the caterpillar. . . . The effect is also greatly strengthened by two pink whips which are swiftly protruded from the prongs of the fork in which the body terminates. . . . The end of...