ACALEPH/E. 



ACALEPH^E. 



observed on the fibres of voluntary muscles. Where these cannot be 

 seen, tissue consisting of a granular substance exists which possesses 

 the peculiar power of contraction. Professor E. Forbes says, that he 

 has " paralysed one side of a Rhizostoma A Idroandi, whose disk 

 measured more than a foot across, by removing with a scalpel the 

 bands of that half, whilst the other side contracted and expanded as 



Phizostoma cerulea (Cnvier). 



usual though with more rapidity, as if the animal were alarmed or 

 suffering." The tentacles of most species are capable of wonderful 

 extension and retraction, movements which must be effected by means 

 of muscular tissue. 



Pood and Jiii/i-nii/in. The food, small fishes and marine animals, 

 both living and dead, is probably conveyed to the mouth not only by 

 the tentacles and cirrhi with which the greater part of the Medueie are 

 furnished, but also by contractions in the umbrella or disk itself. 

 Fishes of some size have been found dead and entangled in the tentacles 

 of Medusa, killed most probably by that benumbing or stinging quality 

 which has obtained for them the name of Sea-Nettles. Professor E. 

 Forbes, speaking of the habits of Sarsia tubidosa, says, "being kept in 

 a jar of salt water with small Crustacea they devoured these animals, 

 BO much more highly organised than themselves, voraciously, appa- 

 rently enjoying the destruction of the unfortunate members of the 

 upper classes with a truly democratic relish. One of them even 

 attacked and commenced the swallowing of a Lizzia octopunctata, 

 quite as good a Medusa as itself. An animal which can pout out its 

 mouth twice the length of its body, and stretch its stomach to corres- 

 ponding dimensions, must indeed be ' a triton among the minnows,' 

 and a very terrific one too." 



By the investigations of M. Milne-Edwards principally, we now know 

 that all the Pulmoyrada have gastric cavities, but all have not -mouths 

 in the ordinary acceptation of the word. In Rhizoatoma, for instance, 

 the only communication between the stomach and the outer surface is 

 carried on through numerous branching canals in the pensile arms. 

 In most cases a system of vessels is observed proceeding directly from 

 the stomach, partly nutritive and partly respiratory, but there does 

 not appear to be any distinct blood-vessels. From the recent researches 

 of Frey, Leuckhart, and E. Forbes, it does not appear that any special 

 blood-fluid exists amongst the species they have examined. 



Repi-'i'li" 'nd Development. Themajority of the Acalephae 



have very distinct reproductive glands. In the Palmor/riiilii they are 

 placed either on the surface of the sub-umbrella, or on the inner and 

 upper-part of the cavity of the peduncle. In most cases these animals 

 ap|>ear to be bisexual, though the two sexes are often united in the 

 same individual; but Milne-Edwards, Wagner, and Will have observed 

 individuals with sperm-cells only, and with germ-cells only. Although 

 probably in all cases reproduction takes place by conjunction of these 

 cellrt, the Mediate, like some other lower animals, have the power of 

 producing their offspring by germination. This fact was first made 

 known by Sara in IM'i. mttMor E. Forbes, in his great work on 

 the British Naked-Kywl Medusae, says, "I have observed four modes 

 of propagation by germination among the Medusae. 1. Germination 

 from the ovaries, as observed by Sars. 2. Germination from the 

 peduncular stomach. 3. Germination from the walls of a tubular 

 proboscis. 4. Germination from the bases or tubercles of the four 

 marginal tentacles in .SV//-.S/" /*/'o///Vnj." In order to suggest the nature 

 of this mode of reproduction, Forbes has the following passage: 

 "What strange and wondrous changes! Fancy an elephant with a 

 number of little elephants sprouting from his shoulders and thighs, 

 bunches of tusked monsters hanging epaulette-fashion from his flanks 

 in every stage of advancement. Here a young pachyderm almost 

 amoq>hous, there one more advanced, but all ears and eyes ; on the 

 right shoulder a youthful Chuny, with head, trunk, toes, no legs, and 

 a shapeless body ; on the left, an infant better grown, and struggling 

 ' away, but his tail not sufficiently organised as yet to permit of 

 . and free fiction ! The comparison seems grotesque and absurd, 

 but it iv;il!\ pi I' : " 'lcT<i:ril>ing HH actually occur- 



ring among our Nakod-Kyc.fi Medusa; ! " 



The history of the development of the ova is not less interesting. 

 When first produced they are retained in the interior of the creature 

 until they are covered with cilia, when they pass out, and are found in 

 the water resembling/!/. 1. In the course of a little time it attaches 

 itself to some fixed object, and then puts out four arms. In the 

 first stage we have an infusorial animalcule ; in the next, fig. 2, we 

 have a rotifer or hydroid polype. Not only have we the resemblance to, 

 but some of these forms have been shewn by Steenstrup ('Alternation 

 of Generations') to have been mistaken for permanent states of other 

 animals. The first four arms are succeeded by four more, fig. 3 : at 

 this stage germs or buds frequently grow from its side, fig. 4 : the 

 polypiform body then lengthens, and at last becomes wrinkled, fig. 5 : 

 depressions appear, and the elongated body is cut up into a series of 



horizontal slices, from the edges of which tentacles grow, fig. 6 : each 

 layer escapes, and presents itself in the form of a young Medusa, fig. 1. 

 Such is the history given by Steenstrup, in one of the common forms 

 of Pulmograde Medusae, and such with modifications appear to be the 

 changes which each ovum of the Medusa passes through before it 

 becomes a fully developed animal. 



Power of Stinying. The name Acalephte, Sea-Nettles, suggests this 

 property. It is not, however, improbable that this function is possessed 

 only by a few species. Some possess this property in a remarkable 

 degree, as the Cyanea capillata, which is a terror to bathers in our 

 seas. At most two or three others possess it in relation to the human 

 skin. It is probable they exert greater power over their prey or their 

 enemies amongst the lower classes. The stinging power is supposed 

 to reside in small capsular hairs, which are found in the tissues of 

 the AcalepJue as well as in Actinia: and other polypes. 



Phosphorescence. On whatever property this phenomenon depends, 

 there is no doubt that it is possessed in a high degree by almost every 

 species of Medmce. The circumstances, however, on which it depends 

 seem to be little known. On some occasions the Aealephce with other 

 marine creatures will give out abundance of light, whilst at other times 

 not a glimmer can be observed. 



The A calephce have been divided into four families : the Pulmoyrada, 

 the Ciliograda, the Cirrhtyrada, and the Physoyrada. The following 

 is the arrangement of the Pulmoyrada given by M. de lilainville, who, 

 by intercalating the genera of Perron and Lesueur, and of Eschscholtz, 

 the existence of which he is far from guaranteeing, gives us the follow- 

 ing synoptic table : 



PULMOGRADA, Or MEDUSARIA. 



SECT. I. Simple. 

 Genera : Eudora, Ephijra, Phorcynia, Eulymene, Charybd<ea. 



SECT. II. Tentaculated. 



Genera : Bereniae, jSifUorea, Mesonema, Poli.rena, jEgina, Ounina, 

 Foveolia, Eurybia, Peyaaia, Obelia. 



SECT. III. Sub-Proboscidean. 



Genera: Oceania, Aglaura, Melicerte, Cytacit, Thawmantias, Tima, 

 Campanella. 



SECT. IV. Proboscidean. 



Genera: Orithyia, Geryonia, Saphenia, Diaium, lAmiiche, Favonia, 

 Lymnorea, Sthenonia. 



SECT. V. Srachideoui and Pedamcutated, 



Genera: Ocyr'ue, Cnesiopca, Anrelia, Mditcea, Evayora, Cepluea, 



Jlliizoitoma, Chrysaora, Pelagia. 



Wo now proceed to lay before the reader examples of these several 

 pectious. 



