The Variation of Animals and Plants Under Domestication. 2 V

The Variation of Animals and Plants Under Domestication. 2 V

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1898 edition. Excerpt: ...their product, --that is, the offspring thus generated. The period of life at which the causes that induce variability act, is likewise an obscure subject, which has been discussed by various authors.'9 In some of the cases, to be given in the following chapter, of modifications from the direct action of changed conditions, which are inherited, there can be no doubt that the causes have acted on the mature or nearly mature animal. On the other hand, monstrosities, which cannot be distinctly separated from lesser variations, are often caused by the embryo being injured whilst in the mother's womb or in the egg. Thus I. Geoffrey Saint-Hilaire 5 asserts that poor women who work hard during their pregnancy, and the mothers of illegitimate children troubled in their minds and forced to conceal their state, are far more liable to give birth to monsters than women in easy circumstances. The eggs of the fowl when placed upright or otherwise treated unuaturally frequently produce monstrous chickens. It would, however, appear that complex monstrosities are induced more frequently during a rather late than during every early period of embryonic life; but this may partly result from some one part, which has been injured during an early period, alfecting by its abnormal growth other parts subsequently developed; and this would be less likely to occur with parts injured at a later period.51 When any part or organ becomes monstrous through abortion: 1. rudiment is generally left, and this likewise indicates that its development had already commenced. Insects sometimes have their antennae or legs in a monstrous condition, the larvae of which do not possess either antennze or legs; and in these cases, as Quatrefages 5' believes, we more

Product details

  • Paperback | 216 pages
  • 189 x 246 x 12mm | 395g
  • United States
  • English
  • black & white illustrations
  • 1236872037
  • 9781236872036