518 CLASS ECHINODERMATA. 
FIFTH AND LAST CLASS OF THE ZOOPHYTES, 
AND OF THE ENTIRE ANIMAL KINGDOM. 
INFUSORIA. 
Iv is customary to place at the end of the animal kingdom, 
some beings so small that they escape the naked eye, and 
which remained undistinguished, until the microscope had, 
in some sort, revealed to us another world. ‘The majority of 
them present a gelatinous body of the most extreme sim- 
plicity, and this, undoubtedly, is their proper place ; but there 
have also been left among the infusoria, some animals much 
more complicated in appearance, and which resemble them 
only in their minuteness, and the habitat in which they are 
usually found. 
Of these we shall make our first order, still, however, in- 
sisting on the doubts which yet remain relative to their 
organization. 
FIRST ORDER OF INFUSORIA. 
ROTIFERA, 
Are distinguished, as we have just said, by a greater degree 
of complication. Their body is oval and gelatinous. A 
