Outlines of comparative physiology : touching the structure and development of the races of animals, living and extinct / by Louis Agassiz and A.A. Gould.

Date:
1851
Catalogue details

Licence: Public Domain Mark

Credit: Outlines of comparative physiology : touching the structure and development of the races of animals, living and extinct / by Louis Agassiz and A.A. Gould. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    6000 species ; and if we consider that wherever any one stra- tum of the earth has been well explored, the number of spe- cies discovered has not fallen below that of the living species which now inhabit any particular locahty of equal extent, and then bear in mind that there is a great number of geological strata, we may anticipate the day when the ascertained fossil species will far exceed the hving species,* § 8. These numbers, far from discouraging, should, on the contrary, encourage those who study Natural History. Each new species is, in some respects, a radiating point which throws additional light on all around it; so that as the pictm’e is en- larged, it at the same time becomes more intelligible to those who are competent to seize its prominent traits. § 9. To give a detailed account of each and all of these animals, and to show their relations to each other, is the taslc of the Naturalist. The number and extent of the volumes ah’eady pubhshed upon the various departments of Natural History show, that only a mere outhne of so vast a domain could be given in an elementary work hke the present, and that none but those who make it their special study can be expected to survey its individual parts. 10,000. There are collections of marine shells, bivalve and univalve, which amount to 5 or 6000; and collections of land and fluviatile shells, which count as many as 2000. The total number of mollusks would there- fore probably exceed 15,000 species. Among the articulated animals it is difficult to estimate the number of species. There are collections of coleopterous insects which number 20 to 25,000 species; and it is quite probable, that by uniting the principal collections of insects, 60 or 80,000 species might now be counted; for the whole department of articulata, comprising the Crustacea, the cirrhipeda, the insects, the red-blooded worms, the intestinal worms, and the infuso- ria, as far as they belong to this department, the number would already amount to 100,000; and we might safely compute the probable number of species actually existing at double that sum. Add to these about 10,000 for radiata, echini, star-fishes, medusae, and polypi, and we have about 250,000 species of living animals; and sup- posing the number of fossil species only to equal them, we have, at a very moderate computation, half a million of species. * In a separate work, entitled Nomenclator Zoologicus,’’ by L. Agas- siz, the principles of nomenclature are discussed, and a list of the names of genera and families proposed by authors is given. To this work those are referted who may desire to become more familiar with nomenclature, and to know in detail the genera and families in each class of the Animal Kingdom. B 2