Zoological classification : a handy book of reference with tables of the subkingdoms, classes, orders, etc., of the animal kingdom, their characters and lists of the families and principal genera / [Francis Polkinghorne Pascoe].

  • Francis Polkinghorne Pascoe
Date:
1880
Catalogue details

Licence: Public Domain Mark

Credit: Zoological classification : a handy book of reference with tables of the subkingdoms, classes, orders, etc., of the animal kingdom, their characters and lists of the families and principal genera / [Francis Polkinghorne Pascoe]. Source: Wellcome Collection.

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    Subclass I. Z0ANTHA11IA. Polyactinia. Polypes with simple or occasionally branched tentacles, sis, or a multiple of six. Corallum, when present, mostly sclerodermic, more rarely sclerobasic. The corallum is a hard, mostly calcareous substance [calcium carbonate], secreted externally in tbe sclerobasic corals, and inter- nally in the sclerodermatous; in the Malacodermata it is, when present, disseminated in the form of small spicules [selerites]. An individual [persona] of the compound corallum is known as a “ corallitethe outer wall forms the “ theca,” the upper part of which is the cup or caliole; below it is often divided radially by distinct vertical septa [mesenteries] united in the centre to the “columella.” Sometimes the thee® are divided by horizontal plates [tabulae], “ Dissepiments ” are incomplete plates growing from tbe sides of the septa. The “ ccenenchyma ” is the calcareous covering uniting the individual corallites together ; it is secreted by the ccenosarc, with which it may be said to correspond. Milne-Edwards divides the Zoautharia into three groups:— Corallum either absent or rudimentary Malacodermata. Corallum present Corallum internal, calcareous Sclerodermata. Corallum external, not calcareous Sclerobasica. Order I. MALACODERMATA. (Sea-anemones.) Helianthoida. Actiniaria. Hexacoralla. Corallum absent, or represented by a few spicules. Tentacles nu- merous, simple. Polypes rarely aggregated. Sexes mostly distinct. In the Zoantbida; only are the polypes united by a coinmpn creeping stem. The majority, owing to their muscular base, enjoy some power of locomotion, although generally adherent to some foreign body. The Ilyanthidie have no adherent base ; and Arachnactis is a free-swimming organism : it is, however, possibly an immature form. The tentacles are generally disposed in two or more series. These are successively developed from within outwards, in multi- ples of six; but one or more tentacles are sometimes abortive. They are often perforate at the end. In Sagartia bellis, a common species, there are six rows, the inner minute, and altogether they amount to about 500. [ Gossc.]