INFUSORIA, 451 
present a sort of palpitation ; the existence of these motions, however, 
is doubted by M. Grant *. 
Sponges assume innumerable shapes, each according to its species, 
and resemble shrubs, horns, vases, tubes, globes, fans, &c. 
Every one knows the 
S. officinalis, or common Sponge, which is found in large 
brown masses, formed of extremely fine, flexible, and elastic 
fibres, perforated with numerous pores and little irregular 
canals, all of which intercommunicate. 
CLASS V. 
INFUSORIA. 
Naturalists usually close the catalogue of the animal kingdom with 
beings so extremely minute as to be invisible to the naked eye, and 
which have only been discovered since the invention of the micros- 
cope has unveiled to us, as it were, a new world. Most of them 
present a gelatinous body of the greatest simplicity, and for these, 
this is undoubtedly the situation; but authors have placed among 
the Infusoria, animals apparently much more complicated, and which 
only resemble them in their minuteness, and the dwelling in which 
they are usually found. 
They will constitute our first order, though we must still insist 
upon the doubts relative to their organization, which are not yet dis. 
sipated +. 
ORDER I. 
ROTIFERA. 
The Rotifera, as above stated, are distinguished by a greater de- 
gree of complication. Their body is oval and gelatinous; we can 
distinguish in it a mouth, a stomach, and intestine, and an anus near 
* M. Audouin and M. Edwards, Ann. des Sc. Nat., XI, pl., xvi, have adopted 
this opinion of M. Grant. 
+ N.B. As the nature of this work does not require me to enter into the endless 
details concerning these infinitely minute beings, and as I can say nothing concern- 
ing them from my own observations, I can only refer the reader to the work of M, 
Bory de Saint Vincent, entitled ‘‘ Essai d’une Classification des Animaur Microsco- 
piques,”’ extracted from the second volume of the Zoophytes, of the Encye. Métho- 
dique, Paris, 1626, where these little animals are divided into eighty-two genera, 
