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 paris of Italy these worms are 
considered agreeable food. 
CLASS III. 
ACALEPHA. 
Our third class comprises Zoophyta which 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 circulation. 
Mepusa, Lin 
The Medusz are furnished superiorly with a disk more or less con- 
vex, resembling the head of a mushroom, and called the wmbella. 
Its contractions and dilatations assist the locomotion of the animal. 
The edges of this umbella, as well as the mouth, or the suckers more 
or less prolonged into pedicles which supply the want 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.5. In the intestines of Seals, and of Birds that prey on Fishes, we find Worms 
very similar to the Ligule, 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 Ligule 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. 
