Aves

Aves

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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. 1907 edition. Excerpt: ...under water; and a tendency to variation chiefly in those parts which carry specific recognition marks. But one may argue that, if the distinctive specific characteristics are to be looked for in the head, there is every reason why the head marks should not vary, and it is certainly hard to see why in any particular part there should be associated at once the necessity for uniformity and a special tendency to variation. One must allow that whereas in the parts which do not show above water the colouring is governed mainly by the necessity for protective invisibility, yet in the parts that do show above the water there is an inherent tendency to vary, from the very fact that the physiological processes leading to pigmentation have become concentrated in them; a concentration which results from the need for recognition marks in the parts that do come easily into view as the penguin floats on the surface of the water. That the under parts should all be white seems naturally to result from the necessity for invisibility from below, where lurk, not only the fish that the bird must catch, but the seals and whales that would prey upon the bird. Whatever may be the reason, the fact remains that the demarcation line between the black and white is seen to vary about the head and neck more frequently than elsewhere. And the only other variation noticed in this species was in the case of the foot illustrated in Fig. 6 of Plate X., where the blackening of the sole was irregular, and also in the extent of the black tip to be seen on the under surface of the wing, which varies within wide limits, and which, being common to several species, cannot be considered of much specific value. There is still one other variation of the Adelie Penguin that...show more

Product details

  • Paperback | 60 pages
  • 189 x 246 x 3mm | 127g
  • Rarebooksclub.com
  • United States
  • English
  • black & white illustrations
  • 1236938186
  • 9781236938183