of any other class of marine animals : they exist 

 in all seas ; and yet we remain very ignorant 

 with regard to several points in their structure 

 and history. The peculiar nature of their 

 tissues, the singular arrangementsof their organs, 

 the anomalies in their functions, present as many 

 objects of interesting inquiry to the physiologist, 

 as the wonderful variety and striking elegance 

 of their forms, and their splendid colouring 

 present to the admiration of the naturalist. 

 Peron,* in his animated description of the Me- 

 dusa, observes, "Among the animals of this 

 family we find the most important functions of 

 life performed in bodies which offer to the eye 

 little more than a mass of jelly. They grow fre- 

 quently to alargesize, so as to measure several feet 

 in diameter; and yet we cannot always determine 

 what are their organs of nutrition. They move 

 with rapidity, and continue their motions for 

 a long time ; and yet we cannot always satis- 

 factorily demonstrate their muscular system. 

 Their secretions are frequently very abundant, 

 and yet the secreting organs remain to be dis- 

 covered. They seem to be too weak to seize any 

 vigorous animal, and yet fishes are sometimes 

 their prey. Their delicate stomachs appear to be 

 wholly incapable of acting upon such food, 

 and yet it is digested within a very short time. 

 Most of them shine at night with great bril- 

 liancy, and yet we know little or nothing of 

 the nature of the agent which produces so re- 

 markable an effect, or of the organs by which 

 it i3 elaborated. And, lastly, many of them 

 sting the hand which touches them ; but how, 

 or by what means, they do so still remains a 

 mystery." It is, therefore, but a very imperfect 

 account of the anatomy and physiology of this 

 class that can be at present given. 



The following are the names and characters 

 of the groups into which the acalephae have 

 been divided by M. De Blainville,f whose 

 arrangement is nearly the same as that adopted 

 by Eschscholtz.J 



I. PHYSOGRADA. Body regular, symme- 

 trical, bilateral, fleshy, contractile, often very 

 long, provided with an aeriferous sac. Bran- 

 chiae in the form of long cirri, very con- 

 tractile. 



1. Organ of natation simple and lamellated. 

 Gen. Physalus. (Physalia, Lam.) 



2. Locomotive organs complex and vesicular. 

 Gen. Physsophora. Diphysa. Rhizophysa. 



3. Locomotive organs in the form of smooth 

 scales, disposed in transverse series. Gen. 

 Stephanomia. Agalma. Protomedea. Rho- 

 dophysa. 



II. DIPHYDA. Body bilateral and symme- 

 trical, composed of a visceral mass of small 

 size and of two swimming organs, hollow, 



' Pcron. Ann. du Mus. xiv. 220. 



Diet, des Sc. Nat. " Zoophytes." 1830. 



System der Acalephen. Berlin, 1829. The 

 most complete treatise on the anatomy and history 

 of the acalepha hitherto published. Its learned 

 author enjoyed excellent opportunities of studying 

 these animals in the course of the two voyages 

 round the world undertaken by Kotzebue, of whose 

 expeditions he was naturalist. 



contractile, somewhat cartilaginous, and placed 

 one before the other, the anterior one being 

 in more direct connexion with the central 

 visceral mass, which it seems to surround ; 

 the other posterior, and very slightly adherent. 

 Mouth at the extremity of a stomach more 

 or less extensile. Anus unknown. A long 

 filamentary organ, ovigerous, rises from the 

 root of the central mass, and is prolonged 

 more or less posteriorly. 



Gen. Cucubalus. Cucullus. Cymba. Cu- 

 boides. Enneagona. Amphiroa. Calpe. 

 Abyla. Diphyes. Ersaea. Eudoxia. Py- 

 ramis. Praia. Tetragona. Sulculeolaria. 

 Galeolaria. Rosacea. Noctiluca. Doliolum. 



III. CILIOGRADA. ( Ctenophora, Esch.) 

 Body gelatinous, free, varying in form, marked 

 on the surface with narrow ambulacra formed 

 by rows of vibratile cilia. Intestinal canal 

 complete, with two orifices.* 



Gen. Beroe. Eucharis. Mnenia. Cal- 

 ymma. Axiotoma. Callianira. Pandora. 

 Medea. Alcynoe. Cestum. Cydippe. Idya. 



IV. PULMOGRADA. ( Discophortf, Esch.) 

 Body entirely gelatinous, circular, without 

 any solid part internally, margin provided 

 with cirri of various forms, or with foliace- 

 ous appendages pendent from the inferior 

 surface. 



1. Simple : without true tentacula, peduncles 

 or arms. 



Gen. Eudora. Ephyra. Phorcynia. Eu- 

 lymene. Carybdea. Euryale. 



2. Tentaculated : the circumference of the 

 body, and sometimes the mouth, surrounded 

 by tentacula. 



Gen. Berenice. Equorea. Foveolia. Pe- 

 gasia. Cunina. ^Egina. Eurybdia. Thau- 

 mantias. Obelia. Linuche. Eirene. 



3. Subproboscic : gastric cavity prolonged 

 into a short peduncle, at the extremity of which 

 is the mouth, surrounded by four brachial 

 appendages. 



Gen. Oceania. Aglaura. Melicerta. Sa- 

 phenia. Tima. 



4. Proboscic: the lower and central part 

 of the body prolonged into a proboscis-like 

 appendage, either simple or provided with 

 arms. 



Gen. Orythia. Geryonia. Diancea. Fa- 

 vonia. Cytseis. 



5. Brachigerous : lower surface furnished 

 with more or less numerous appendages, bra- 

 chial, ramified. 



Gen. Ocyroe. Cassiopea. Medusa (Au- 

 relia of Peron). Callirhoe. Melitea. Eva- 

 gora. Cephea. Rhizostoma. Chrysaora. 

 Cyanea. Pelagia. Sthenonia. 



V. CIRRIGRADA. (Velellida, Esch.) 



* M. De Blainville regards the animals included 

 in this and the two preceding sections as being 

 more allied in structure to the Mollusca, (his Mala- 

 cozoaires,) than to the Radiata, with which they are 

 arranged by most zoologists. Accordingly he sepa- 

 rates them from the two succeeding sections, which 

 are truly radiate animals, and of which he forms 

 a class in his great division Actinoxoaires, under the 

 name of Arachnodenna. 



