Alternating Generations: A Biological Study of Oak Galls and Gall Flies

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Clarendon Press, 1894 - 198 páginas

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Página 203 - A New English Dictionary, on Historical Principles: founded mainly on the materials collected by the Philological Society. Edited by James AH Murray, LL.D., with the assistance of many Scholars and men of Science.
Página xxxii - If it could be proved that any part of the structure of any one species had been formed for the exclusive good of another species, it would annihilate my theory, for such could not have been produced through natural selection.
Página iii - IDs. 6d. net. Aldis. A Text-Book of Algebra : with Answers to the Examples. By WS ALDIS, MA Crown 8vo, 7*.
Página xxxv - an active growth of cells" around the larva, much to that larva's advantage. Now surely it is too much to ask us to believe that the germplasm of the plant, in the first instance, before even, say, a single Cynips had visited it, had in the complex collocation of its molecules, an arrangement such as would compel the plant which was to grow from it, to grow these cells and form a gall...
Página xvi - ... germ-cell, or in other words, of the germ-mass unchanged in the body of the first individual developed from that germ-mass, with so much of the spermatic force inherited by the retained germ-cells from the parent-cell or germ-vesicle as suffices to set on foot and maintain the same series of formative actions as those which constituted the individual containing them.
Página xxxviii - In these galls and other similar diseases in plants we have, it seems, hundreds of specific diseases -due to as many hundreds of specific morbid poisons ; for the most reasonable, if not the only reasonable, theory of these diseases is, that each insect infects or inoculates the leaf or other structure of the chosen plant with a poison peculiar to itself.
Página xxxiv - ... its young, and none ever pricks a bud the second season, or lives to know the results that follow the act. Natural selection alone has preserved an impulse which is released by seasonally recurring feelings, sights, or smells,* and by the simultaneus ripening of the eggs within the fly. These set the whole physiological apparatus in motion, and secure the insertion of eggs at the right time and in the right place. The number of eggs is instinctively proportionate to the space suitable for oviposition,...
Página 99 - ... altered appearance, and new cell formation begins freely, leading to a thickening of the surrounding leaf surface. After the lapse of about fourteen days the green and red-shaped gall is fully grown. If it be now opened the egg can still be seen lying within the cavity. The embryonic development is as yet unfinished and three weeks elapse before the larva emerges from the egg to find around it the material prepared for its nutriment. In this case the wound caused by the fly is the immediate exciting...
Página 99 - ... after a careful observation on Nematus Vallisnierii, says: "This fly, which is armed with a finely serrated terebra, cuts into the tender leaves of the end of the shoot of the Salix amygdalina, and inserts her egg into the open wound, frequently placing several in the same leaf. At the same time the glandular secretion flows into the wounded leaf. A few hours after this injury the leaf surface presents an altered appearance, and new cell formation begins freely, leading to a thickening of the...
Página xv - On the Alternation of Generations ; or, The Propagation and Development of Animals through Alternate Generations, a peculiar form of fostering the young in the lower classes of animals.

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