SIMPLICLL 651 



ating in tlie stomach, and proceeding by ramifications toward the circumference. Another species, C. e&rysa 

 lias tlie margin furnished with long tentacnla, and rows of brown or yellow spots, forming rays on the convex 



surface. It is very common, and there are great varieties in the spots. 



Cuvier distinguishes under the name of 



RlIIZOsTOMA, — 



Those Medusa which have no central opening or month, and which are thence supposed to draw their 

 nourishment by suction by the ramifications of the peduncle, or by the tentacula. They have four 

 ovaries or more. 



Rhizontoma, properly so called, have a central peduncle, more or less ramified according to the species. The 

 vessels w Inch an>e in the small protuberances of the peduncle, unite in a cavity at its base ; and from this, other 

 vessels are ramified to all parts of the umbrella, or disc. The most common species is the blue Bhizostoma, w Inch 

 is often left on sandy shores by the ebbing tide. The umbrella is sometimes two feet in diameter. The peduncle 

 is composed of four pairs of arms, which are very much branched and toothed, and each is furnished with two 

 auricles or appendages at the base, which are also toothed. A tine network of vessels, occupying the thickness of 

 the margin, extends all round the umbrella. According to the obsen atiODS of MM. Audouin an. I Milne Bdwards, 

 these Medusa? are social, or at least they are always met w ith in numerous shoals, swimming in the same direction, 

 and with the body obliquely inclined. 



The Cephe<e of Peron di Iter from the other Rhizostoma only by having filaments intromixed with the denta- 

 tions, or papilla.' of the peduncle. The Cassiojieice have no peduncle ; and their arms, which are usually eight in 

 number, and sometimes branched, rise directly from the under surface. 



Astoma, — 

 Might he the general name for those which have no central mouth, no ramifications of the peduncle, 

 and no cavities for the ovaries. 



Some, however, have the peduncle furnished on each side with filaments that may act as suckers. Others have 

 ho filaments, but the extremity of the peduncle is hollowed out like a funnel, which seems to be the sucker, as 

 from it vessels ascend the peduncle, and others are ramified from its base all over the body. Others again, want 

 the funnel-shaped membrane, or it may have been mutilated before the specimens were obtained. There are still 

 others, which have no vestige of a peduncle; but merely little suckers distributed over the under surface, on the 

 bins of the vessels which are ramified below it ; [and these suckers are, of course, so many little mouths]. Some 

 have no Vestiges of suckers or any other external apparatus, but have both sides smooth ; and there are yet others 

 which have no trace even of internal vessels. The under surface of these is usuall] concave, and may act as a 

 Stomach! These last are very simple animals, and diner from Hydra in scarcely anything but size. 



Beroe. 



This genus should he separated entirely from the Medusae. It has a globular body, provided with 

 salient ribs, extending from the centre of the upper surface to that of the under, and bristled with 

 points or filaments, which appear to be connected with vessels in which there is some appearance of a 

 fluid circulating. The month is on the one extremity, and leads to a Btomach, which occupies tlie 

 of the body. There are also on the sides two organs, which are probably analogous to what are con- 

 sidered the ovaries of the Medu 



B.pileus, a species very common in the Channel, has the body spherical, with eight ribs, and two ciliated 

 tenia, Hi;,, which become verj long bj prejection "f their inferior extremities. MM. Andonin and Milne Bdw 

 have described it-- natural organization with considerable minuteness, and havi traced varii 

 but wit Ik mt being able very clearl) to explain their functions. This »] understood to constitute great part 



of the food of the ci mi mon \\ bale. Naturalists have referred to the same genua verj simple species, whii h ■ onsist 

 of only a sac, furnished with cilia, and open at both ends. The Doliolum of t uto inn e not t\ en projecting ribs, 



but resemble barrels without bottoms. 



I Uiianirttot Peron, differ from Beroe only in having the ribs more salient, and united two and two, so as to 



form two sets of a sort of wings. Jiuuni, resemble the last; but they have upon each tide three long Ciliated 



ribs, and two filaments. Alebuutf, have a cylindrical body, open at the one em i. ami two largi the other, 



which when folded up COmpletelj co\ ,r the body. I he c\ lindrical part is marked with lour salient ribs, which 



end in points, and have eight braces of cilic Oeyroas, have similar wings; but they have no ribs, and only 



four row.-, of Cilia; on the c\ limb ical portion. 



ClSI DSC, — 



Bears, perhaps, the nearest resemblance to Beroe than to any other genua. It is a vary lung gelatin 

 ribbon, having one «i the tides furnished with two rows of alias, and there arc fainter l the same 



on the other side: the month i-< in tlie middle of the inferior edge, ami the stomach is embodied in tlie 



gelatinous substance of the ribbon; from the anal extremity there pn I vessels which ramifj toward 



both extremities of tlie ribbon ; and near the sides of the mouth there arc two \. --, || whii ii pro- 



