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 Sj)onge, 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 tliem 

 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 

 vipon the doubts relative to their organization, which are not yet dis- 

 sipated f. 



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. Audouiu and M. Edwards, Ann. des Sc. Nat., XI, pi., xvi, have adopted 

 this opin'.on of M. Grant. 



f N.B. As the nature of this work does not require me to enter into the endless 

 details concerDing these infinitely minute beings, and as I can say nothing concern- 

 ing them from ray own observations, I can only refer the reader to the work of M. 

 Bory de Saint Vincent, entitled " Essai d'une Classification des Animciux Microsco- 

 piques," extracted from the second volume of the Zoophytes, of the Encyc. Metho- 

 dique, Paris, 1626, where these little animals are divided into eighty-two genera. 



