418 INFUSORIA. 
CLASS V. 
INFUSORIA. 
Naturalists usually close the catalogue of the animal king- 
dom with beings so extremely minute as to be invisible to 
the naked eye, and which have only been discovered since 
the invention of the microscope 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, ani- 
mals apparently much more complicated, and which only re- 
semble 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 dissipated(1). 
(1) 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 con- 
cerning 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 Animaua 
Microscopiques,” extracted from the second yolume of the Zoophytes, of the En- 
cyc. Méthodique, Paris, 1826, where these little animals are divided into eighty- 
two genera. 
