. The animal kingdom : arranged after its organization; forming a natural history of animals, and an introduction to comparative anatomy. Zoology. EADIATA.— 683 CLASS The classification of this group proposecl by Cuvier was founded upon a very imperfect acquaintance ?with the animals it includes ; and it is now altogether abandoned. Much remains to be known, how- ever, with respect to the internal structure of many of the tribes with whose external forms we are familiar ; and it is probable that no classitication yet proposed will remain without considerable modi- fication
. The animal kingdom : arranged after its organization; forming a natural history of animals, and an introduction to comparative anatomy. Zoology. EADIATA.— 683 CLASS The classification of this group proposecl by Cuvier was founded upon a very imperfect acquaintance ?with the animals it includes ; and it is now altogether abandoned. Much remains to be known, how- ever, with respect to the internal structure of many of the tribes with whose external forms we are familiar ; and it is probable that no classitication yet proposed will remain without considerable modi- fication from future discoveries. That which is at present most generally received is based on the mode of locomotion peculiar to the different tribes ; according to which the class is divided into the lour orders, Pulmograda, Ciliograda, Cirrhigrada, and Physograda. I. The order Pclmograda, or :, including all the ordinary Meduste, Is characterized by the re^lar discoidal or circular form of the animals composing it. The body is of gelatinous texture, without any in- ternal solid skeleton ; the stomach is placed under the centre of the disk, and usually opens by a single central mouth ; round the stomach are placed the ovaries, opening by separate aper- tures ; the margin of the disk is usually furnished with cirrhi or tendril-like appendages, but these are not extensible nor contrac- tile ; whilst from the centre of the disk there usually proceeds another set of appendages, which sometimes take the form of separate tentacula (as in the accompanying figure), but are fre- quently united into a sort of proboscis which forms a prolonga- tion of the mouth. The body moves through the water by a sort of flapping movement of the disk, wliich is fui-nished with mus. cular fibres. This order is again subdivided by Professor E. Forbes (On the British Naked-eyed Medusae) into two sub-orders, the SUganoi'ihalmnia, or hooded-eyed, and the Gynmopthalmata, or naked-eyed ; the former con
Size: 1338px × 1869px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorwe, bookcentury1800, bookdecade1860, booksubjectzoology
