Encyclopaedia Britannica > Volume 3, Anatomy-Astronomy

A
NIMAL KINGDOM.
193
Animal Such are the great outlines of a system which, consi-
Kingdom dered in its generality, is certainly the most satisfactory
.11 which has yet appeared. Particular departments may
Acule ^ave been UP> modified, and perhaps improved by
ingenious observers, sedulous within a limited sphere (and
of these ameliorations we shall be careful to avail our¬
selves when we come to enter upon a detailed view of
each of the classes of the animal kingdom); but the con¬
struction and position of the principal groups, their real as
well as relative characters, are developed in the system of
the great French anatomist, in a manner more clear and
accordant with nature than in any other yet promulgated.
We shall therefore in the course of this work adhere,
with some slight transpositions, the reasons for which will
be stated in their proper place, to the classes of Baron
Cuvier. The greater extent and importance of some of
these, in comparison with others, will induce us to bestow
more attention and a larger space to their illustration;
and as certain of the primary divisions, such as the Mol-
lusca and Radiata, contain a greater number of classes, if
not of less importance, at least by no means so strongly
characterized or contradistinguished from each other as
are those of the vertebrated tribes, we shall, in presenting
the history and nomenclature of such classes, group them
together in such a manner as to exhibit them to the
reader either under one of the great primary divisions, or
as an intermediate subdivision, containing one or more
classes. For example, the article Mollusca of this work
will present consecutively under a single head the history
and classification of the six classes contained in the se¬
cond primary division so named;—but the four classes of
vertebrated animals will be each discussed in a separate
treatise. Thus mammiferous animals, birds, reptiles, and
fishes, will form the articles Mammalia, Ornithology,
Reptilia, and Ichthyology. The Classes of the third
primary division, viz. Annelides, Crustacea, Arachnides,
and Insecta, will (with the exception of the first, referred
to Helminthology) likewise be treated of under distinct
heads, in the alphabetical order, of the following terms :— Animal
Crustacea, Arachnides, and Entomology. In regard Kingdom
to the fourth primary division, that of the radiated ani- Jl
mals, commonly called Zoophytes, the first class, named AniI?ia1'
Echinodermata, will be treated of separately under its t
own title; the second class, Entozoa, wdiieh contains the
intestinal worms, will be grouped with the Annelides or
red-blooded worms (as above excepted from the third
primary division) ; and these two classes will be treated of
together under the article Helminthology. The re¬
maining classes of the Animalia Radiata, that is to say, the
Acalephae, the Polypi, and part of the Infusoria, as they
form the last links of the animal kingdom, will come to be
discussed with greater propriety at the concluding stage
of this work, under the head of Zoophytes. Finally, that
portion of the infusorial class which we have excepted in
the above distribution will be found described in the pre¬
sent volume under the word Animalcule. This com¬
pletes the exposition of our zoological system.
The following enumeration exhibits a view of the terms
under which the principal subjects of zoology will be ex¬
plained and illustrated in the course of this work.
Systematic Arrangement.
Mammalia.
* Ornithology.
Reptilia.
Ichthyology.
Mollusca.
Crustacea.
Arachnides.
Entomology.
Echinodermata.
Helminthology.
Zoophytes.
Animalcules.
Alphabetical Arrangement.
Animalcules.
Arachnides.
Crustacea.
Echinodermata
Entomology.
Helminthology.
Ichthyology.
Mammalia.
Mollusca.
Ornithology.
Reptilia.
Zoophytes. (j. vv.)
Animal Magnetism. See Magnetism, Animal.
ANIMALCULE.
Animalcule, a diminutive term (from the word ani¬
mal), applied by naturalists to those minute beings which
become apparent in various fluids when subjected to the
microscope. They were named infusory animals {Infuso¬
ria) by Muller, one of the most celebrated observers in
this department of zoology; and the appellation, however
inapplicable, now occurs in the majority of scientific pub¬
lications. Of course it applies with propriety only to such
species as are developed through the medium of infused
substances. Now we know, that of 400 species of Infuso¬
ria (commonly so called) described by Muller himself, not
a sixth part were observed in any kind of infusions ; whilst
the remainder inhabited the most translucent waters, and
speedily died when placed in impure or corrupted liquids.
Even the word animalcule (or little animal) does not con¬
vey a positive or sufficiently restricted idea in relation to
this particular class; because mites and certain polypi
are extremely minute in their dimensions, and equally re¬
quire the aid of microscopical investigation ; and thus the
term microscopies {microscopiques), recently proposed by
M. Bory de St Vincent, is not less faulty than its prede¬
cessors. The size of an animal, in fact, bears no essential
relation to the other conditions of its organization; and
therefore we cannot infer its nature with any certainty
from a knowledge of its dimensions. At the same time it
must be admitted, that the most simply organized, both of
plants and animals, are also the most minute; and thus
the Infusoria may be regarded as possessed of certain cha¬
racters in common. We here adopt the word Animalcule,
chiefly because it is the most familiar to the English
reader.
The subjects of our present observations may be thus
defined:—Animals invisible to the naked eye ;1 more or less
translucent; unprovided with members (the caudal, and
other appendices, with which certain species are furnished,
being scarcely regardable as such); no perceptible eyes;
contractile in whole or in part; endowed with the sense
of touch ; deriving nourishment by absorption ; generation
(when not apparently spontaneous, and consequently in¬
comprehensible) effected by division, or by the emission of
gemmules or oviform bodies ; inhabitants of liquids. They
are the smallest and most simple of living creatures, but
not less perfect than the other tribes; for though they
possess the fewest faculties, their means are in every way
adequate to their wants, and their vital energies propor¬
tioned to their sphere of enjoyment.
Among microscopical animals we find many species
which, in their aspect and structure, present no analogy
1 The Volx^ox globator, and a few others, which are just discernible without the aid of a microscope,
character.
form exceptions to the above
2 B
VOL. III.