The geographical and geological distribution of animals / Angelo Heilprin.

  • Angelo Heilprin
Date:
1894
Catalogue details

Licence: Public Domain Mark

Credit: The geographical and geological distribution of animals / Angelo Heilprin. Source: Wellcome Collection.

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    according to Moseley, they would seem to prefer a habitation near the mouths of fresh-water streams, being seen to crowd up towards the heads of fjords and inlets. In the Hawkesbury inlet, New South Wales, the Scyphomedusse were observed by this naturalist swimming in shoals where the water was so pure as to be quite drinkable. Much uncertainty still exists as to the relation which the free oceanic fauna bears to the fauna of the deep-sea, an uncertainty due to the difficulty of determining the actual depth whence the different organisms caught in the net were obtained. Alexander Agassiz maintains, as the result of experiments made with the Sigsbee net, the most improved appliance thus far invented for the purposes of deep-sea exploration, that “the surface-fauna of the sea is really limited to a comparatively narrow belt in depth [about fifty fathoms], and that there is no intermediate belt, so to speak, of animal life between those animals living on the bottom or close to it, and the surface pelagic fauna.”47 Beyond a depth of one hundred fathoms nothing was found. On the other hand, the numerous observations made by Mr. Murray on board the “Challenger,” with appliances less perfect than those used by Mr. Agassiz, almost conclusively prove that the depth penetration is very much greater than is here indicated, and that possibly a direct continuation exists in the case of certain groups of animals between the pelagic and abyssal faunas. The fact seems to be pretty satisfactorily established, however, that the true zone of free oceanic life, or that which is most numerously inhabited, is a shallow one, and that whatever life extends to great depths is comparatively restricted. It would appear that a large proportion, if not the greater num- ber, of the pelagic animals are more or less nocturnal in their habits, shunning the glare of daylight, and appearing on the actual surface only during the hours of evening and night. Such are most of the pelagic fishes, crustaceans, pteropods, heteropods, and fora- minifers, which in their hidden depths for a long time eluded the search of naturalists. The radiolarians, jelly-fishes, and certain crustaceans, on the other hand, seem to prefer the open daylight, appearing at all hours on the surface during calms; and the same is the case with a number of fishes, as the flying-fish and dolphin (Coryphsena). There is thus a perpetual oscillation in this upper