PULMOGRADA.- 



-RADIATA.- 



-ClLIOGRADA. 



397 



irjstance) out of the water, ami lay it on a board or 

 dry stone, it deliquesces so rapidly, that an individual 

 weighing fifty ounces when taken out of the sea, has 

 been found in no great length of time to leave nothing 

 bt'liind but a little dry cellular tissue weighing no more 

 than five or six grains ! Tlieir organs aie arranged in 

 ray-lilie processes radiating from a common centre or 

 a longitudinal axis, in which are lodged the digestive 

 organs. Tlieir body is surrounded by a very delicate 

 epidermis ; and on the arms, tentacles, and other parts 

 of the body, there exist a number of cilia and peculiar 

 prehensile organs, which produce when handled a 

 stinging sensation like that of nettles. These are 

 generally known by the name of nettling organs ; and 

 it is from this stinging property that the Acalephs have 

 acquired the name of Sca-netths. 



These creatures are in general of small size, only 

 rendered obvious, indeed, to the naked ej'e by another 

 property they possess — that of their phosphorescent 

 luminosity. Some, however, are of considerable dimen- 

 sions, and as seen at night far out at sea, appear like 

 glubes of fire or cannon balls heated to incandescence, 

 rolling along far below the keel of the ship. Some of 

 them are hermaphrodite or bisexual, while others are 

 of one sex alone. They are propagated by eggs, and 

 according to the plan of what is known as the alter- 

 nation of generations. The eggs produce a series of 

 young which at first resemble infusory animalcules. 

 These little creatures become fixed after a time, and 

 assume a polyp-like form, which gives birth by gemma- 

 ation to a new progeny, which ultimately assumes the 

 original form. Tliey also multiply their kind by gem- 

 mation alone, little ones springing out almost ready- 

 made fi'om the substance of their parents, chiefly from 

 the walls of the peduncle, or the surface of the 

 ovaries, and closely resembling the parent from which 

 they sprung. 



The species of Acalepha; are numerous ;* elegant 

 pellucid beings, of varied hues, and diverse forms, float- 

 ing on or near the surface of the water, and moving 

 with a considerable variety of modes of locomotion. 



We arrange them in four orders, and this diversity 

 in their method of progression forms an excellent basis 

 for their classification. These four orders are — 



I. Pulmograda, or Discophora, containing the 

 Jledusre, &c. 



II. Cillogi'ttda, or Ctenopliora, containing tlie Be- 

 roes, &c. 



III. Cirrltigrada, contai-jing the Velellse and Por- 

 pitte, &c. 



IV. Fhijsograda, containing the Physaliie and 

 Diphyida;. 



Order I.— rULMOGRADA ok DISCOPHORA. 

 The animals belonging to this order of Acalepha; are 



• Some of the smaller kinds are very abimtlant in the northern 

 eeas. Scoresby tells us that they are found chiefly in those por- 

 tions of the sea where the water was of an olive-green colour. 

 The number, he says, was found to be immense. *' They were 

 about one-fourth of an inch asunder. In this proportion a cubic 

 inch of water must contain 64; a cubic foot 110,592; a cubic 

 fathom 23,887,882 ; and a cubic mile about 23,888,000,000,000 1 

 Provided the depth to which they extend be but 250 fathoms, 

 the above immense number of one species may occur in a space 

 of two miles square." 



generally known by the name of Medtisiv, " Sea-blub- 

 bers, or Jelly-fishes." Their motion through the water 

 is ell'ected by means of a powerful contraction of the 

 body, by which the water contained in its hollow is 

 expelled ; and by thus alternately dilating and contract- 

 ing the body, the animals are enabled to propel them- 

 selves with tolerable rapidity. 



The Medusae are entirely gelatinous, consisting of a 

 large hemispherical disc, more or less convex above, 

 very much like a mushroom or an umbrella. They 

 have no solid axis, but have an elongated peduncle 

 suspended from the inner surface of the umbrella, in 

 which is situated a simple central stomach ; and the 

 margin of the disc is furnished with long tentacula, 

 which hang down from it in the water. The pellucid 

 nature and hemispherical form of the Medusa; have 

 often caused them to be likened to glass globes and 

 lamp glasses. 



The Pulmograde Acalephs or Medusse are divided 

 into two groups or sub-orders : 1st. The Hooded- 

 EYED Medus.e or Phanerocaiqiie ; and 2nd. Tlie 

 Naked-eyed Medus.b, or Cryptocarpse. 



To the first sub-order (Plianerocarpce) belong the 

 tnte Medusa;, and these again have been divided into 

 several families. 



The family Elilzosloraldie is represented in Plate 2, 

 fig. 4, by the species Rhkostoma Cuvlcrll, an inhabi- 

 tant of the European seas. 



The family Medmldce is represented in Plate 2, 

 fig. 1, by the Medusa (Cyanea) aiirlta, a native of 

 European seas ; in Plate 2, fig. 3, by the Pehigia jila- 

 iwspira. 



The second sub-order (the Cryjitocarpce) or Naked- 

 eyed Medusa; contains numerous species. The British 

 species have found an able historian in the late Profes- 

 sor E. Forbes, who in his excellent memoir, published 

 by the Ray Society, has described upwaids of forty 

 found on our shores. 



The family Geryonildee is represented in Plate 2, 

 fig. C, by Geroiiyahexapih)jlla. 



The family Berenlcldce is represented in Plate 2, 

 fig. 5, bj' Berenice rosea. 



The iixmWy 2Equorel doe \s represented in Plate 1, fig. 

 9, by the JE<piorea Forskaellna—& native of the Medi- 

 terranean and Atlantic seas. 



OnDER II.— CILIOGRADA or CTENOPHORA. 



The animals belonging to tl is order of Acalephs 

 are well represented by the curious creatures known 

 by the name of Beroes. Their motion through the 

 water is effected by means of numerous small vibratile 

 cilia, disposed in rows upon the sides of the body. 



There are several families belonging to this order. 

 The family BiroldcP or True Beroes is represented in 

 Plate 1, fig. 1, by the species Bcroe niacrostoma. 



The family Calllanirlda: is represented by a species 

 of Janira {J. hexogona), Plate ], fig. 2. 



Gencs Cestem. — This genus is an aberrant form of 

 this order, but connected to the other members of it by 

 a succession of intermediate links. It is represented in 

 Plate 1, fig. 6, by the only species belonging to it, 



