SIMPLICIA. 421 



They inhabit the abdomen of certain Birds, and particularly of 

 various fresh- water Fishes, enveloping and constricting their intes- 

 tines to such a degree as to destroy them. At certain periods they 

 even perforate the parietes of their abdomen, to leave it. One of 

 them, 



L. abdominalis, Gm. ; L. cingulum, Rud.; Goetz., XVI, 4 — 6, 

 inhabits the Bream *. In some parts of Italy these worms are 

 considered agreeable food. 



CLASS III, 



ACALEPHA. 



Our third class comprises Zoophyta Avhich swim in the waters of 

 the ocean, and in whose organization we can still perceive vessels, 

 which, it is true, are generally mere productions of the intestines ex- 

 cavated in the parenchyma of the body. 



ORDER I. 



SIMPLICIA. 



The simple Acalepha float and swim in the ocean by the alternate 

 contractions and dilatations of their body, although their substance is 

 gelatinous and without any apparent fibres. The species of vessels 

 observed in some of them are hollowed out of their gelatinous sub- 

 stance ; they frequently and evidently originate from the stomach, 

 and do not occasion a true circvilation. 



Medusa, Lin^ 

 The MeduScT are furnished superiorly with a disk more or less con- 

 vex, resembling the head of a mushroom, and called the umbella. 

 Its contractions and dilatations assist the locomotion of the animal. 

 Tlie edges of this umbella, as well as the mouth, or the suckers more 

 or less prolonged into pedicles which supply the Avant of it, in the 

 middle of the inferior surface, are furnished with tentacula of various 



* For the others, see Rud., Hist., II, p. II, p. 12, and Syn., 132. 



N.B. In the intestines of Seals, and of Birds that prey on Fishes, we find Worms 

 very similar to the Ligulje, but with genital organs, and even a head analogous to 

 that of the Bothryocephali. M. Rudolphi supposes that these Worms of Birds are 

 the same as the Ligul* of Fishes, which can only acquire their full development 

 after they have passed from the abdomen of the latter into the intestines of the 

 former. 



