A manual of physiology : including physiological anatomy / by William B. Carpenter.

  • William Benjamin Carpenter
Date:
1856
Catalogue details

Licence: Public Domain Mark

Credit: A manual of physiology : including physiological anatomy / by William B. Carpenter. Source: Wellcome Collection.

    115/690 (page 83)
    134. Now although, as appears from the foregoing general state- ments, the number of species of Crustacea inhabiting the colder seas bears a very small proportion to that which is found within the tropics, and although the species formed to inhabit cold climates are so far inferior both as to size and as to perfection of development, yet it does not follow that the same proportion exists in regard to the relative amount of Crustacean life in the two regions; for this depends upon the multiplication of individuals. In fact it may be questioned whether there is any inferiority in this respect; so abun- dant are some of the smaller species in the Arctic and Antarctic, as well as in the Temperate seas. Thus we see that a low range of temperature is as well adapted to sustain their life, as a higher range is to call-forth those larger and more fully-developed forms, which abound in the tropical ocean. There is an obvious reason why the seas of the frigid zones should be much more abundantly peopled than the land; the mean temperature of the former being much higher than that of the latter. And it would almost seem as if Nature had intended to compensate for the dreariness and desola- i tion of the one, by the profuseness of life which she has fitted the i other to support. I 135. The influence of Temperature in producing a variation in the size of individual Animals of any one species, is not so strongly marked as it is in the case of Plants; for this reason, perhaps, that an amount of continued depression or elevation, which might be ! sustained by a Plant, but which would exert a modifying influence lupon its growth, would be fatal to an Animal formed to exist in ;the same climate. Instances are not wanting, however, in which such a modifying influence is evident; and these, as might be anti- icipated, are to be met-with chiefly among the cold-blooded tribes. .Thus the Bulimus rosaceus, a terrestrial Mollusk, is found on the 'mountains of Chili of a size so much less than that which it attains on the coast, as to have been described as a distinct species. And the Litiorina ■petroia found on the south side of Plymouth Break- j water, acquires, from its superior exposure to light and heat (though perhaps also from the greater supply of nutriment which it obtains), twice the size common to individuals living on the north side within the hai'bour. — The following circumstance shows the favourable influence of an elevated temperature, in producing an unusual pro- lificness in fish ; which must be connected with general vital activity. Three pairs of Gold-fish were placed, some yeai's since, in one of the engine-dams or ponds common in the manufacturing districts, into which the water from the engine is conveyed for the purpose of being cooled: the average temperature of such dams is about 80°. At the end of three years, the progeny of these Fish, which were accidentally poisoned by verdigris mixed with the refuse tallow from the engine, were taken out by wheelbarrows-full. It is not impro- bable that the unusual supply of aliment, furnished by the refuse g2