BOOK FIRST. 
INFUSORIA AND RHIZOPODA. 
CLASSIFICATION. 
§ 3. 
Tux Infusoria, using this word in a restricted sense, are far from being 
the highly-organized animals Ehrenberg has supposed. In the first place, 
on account of their more complicated structure, the Rotifera must be quite 
separated from them, as has already been done by Wiegmann, Burmeister, 
R. Wagner, Milne Edwards, Rymer Jones, and others. The same may 
be said off the so-called Polygastrica. In fact, a great number of the 
forms included under OClosterina, Bacillaria, Volvocina, and others placed 
by Ehrenberg among the anenteric Polygastrica, belong, properly, to the 
vegetable kingdom. Indeed, this author has very arbitrarily taken for 
digestive, sexual, and nervous organs, the rigid vesicles, and the colored 
or colorless granular masses, which are met with in simple vegetable forms, 
but which are always absent in those low organisms of undoubtedly an 
animal nature. Cell-structure and free motion are the only two character- 
istics in common of the lowest animal and vegetable forms; and since 
Schwann © has shown the uniformity of development and structure of 
animals and plants, it will not appear strange that the lowest conditions 
of each should resemble each other in their simple-cell nature. As to 
motion, the voluntary movements of Infusoria should be distinguished 
from those which are involuntary, of simple vegetable forms; a distinction 
not insisted upon until lately. Thus, in watching carefully the motions of 
Vorticellina, 'Trachelina, Kolpodea, Oxytrichina, &¢., one quickly per- 
ceives their voluntary character. The same is true of the power of con- 
tracting and expanding their bodies. 
But in the motions of vegetable forms other conditions are perceived - 
and there is no appearance of volition in either change of place or form, 
their locomotion being accomplished either by means of cilia, or other 
physical causes not yet well understood. Cilia, therefore, belong to 
vegetable as well as to animal forms, and in this connection it is not a little 
remarkable that in animals they should be under the control. of volition. 
With vegetable forms these organs are met with either in the shape of 
ciliated epithelium, as upon the spores of Vaucheria,” or as long, waving 
filaments, as upon che earlier forms of many conferve,® in which last can 
1 Mikroskopische Untersucl , &c. Berlin, teurs des spores des Algues. Ann. des Sc. Nat 
39 Botan. 1843, XIX. p. 266, Pl. XI. fig. . 
2 Thuret. Recherches sur les organes locomo- 8 The same. Pi. X. ee 
