a a le 
Vermes. O. F. Miiller, and after him, Gmelin, 
made a distinct order of them ; and as the greater 
number of the species which Miller investigated 
were found in liquids in which vegetable or ani- 
mal matters had been infused, he gave them the 
name Infusoria. Dr. Ehrenberg of Berlin—who 
has contributed more than even Miller himself 
to our knowledge of the infusory animalcules, 
having up to 1835 examined 722 species—regards 
all true Infusoria, even the smallest monads, as 
organized animal bodies, provided with a mouth 
and internal nutritive apparatus; and he sepa- 
rates the genera Cercaria and Vibrio from the 
true Infusoria, because these genera have neither 
internal stomachs, nor external cilia. Many nat- 
uralists deny the existence of an alimentary canal 
in Infusoria; but Ehrenberg stoutly maintains 
it, and also that of a respiratory system. At 
times, he says, the intestinal canal of the animal- 
cule extends, at the expense of the ventral sacs, 
| so far that it occupies the whole space of the 
body. In Plate IIL, Figs. 13, 14, and 15 are 
| ideal figures of the Loxodes bursaria, in various 
| states of the extension of the alimentary canal, 
and its inner circular motion: a marking the 
| mouth; 6, the alimentary canal; ¢, the ventral 
| sacs; and w the anal aperture. 
There i is no certain law with regard to the pe- 
| culiar species produced by any particular infu- 
sion. In general, several different species will 
be exhibited, which disappear, and are succeeded 
_ by others; and sometimes, where there are my- 
| riads of one kind, a single solitary animalcule of 
a remote genus is found among them, Vinegar 
_ is full of minute eels, which are also found in 
paste. Miller conceives that the sea abounds 
in animalcules peculiar to itself; and Spallanzani 
observes that vegetable substances, dissolving in 
sea-water, produce swarms of animalcules. It is 
possible, that, on carefully attending to the dif- 
ferent seasons of the year, the existence of vari- 
ous species of animalcules may be found dependent 
on them. The red snow of the Arctic regions 
| 1s now known to receive its colour from the pre- 
sence of myriads of animalcules; and green snow 
owes its colour to the same cause: the granules 
being red when young, and green when old. 
The extraordinary minuteness of animalcules 
surpasses the conception of the human mind. 
Leeuwenhoek calculates that the size of some is to 
that of a mite as a bee is to a horse; an hundred 
others will not exceed the thickness of a single 
hair ; and ten thousand of a different species may 
be contained in the space occupied by a grain of 
sand. Ehrenberg has described species so minute 
that a single drop of water may hold 500,000,000. 
The shapes of animalcules are infinitely diversi- 
fied. Let one suppose himself transported to a 
region where the appearance, figure, and motion 
of every animal is unknown, and he will form 
some idea of the variety presented by a drop of 
an infusion presented to the microscope. One 
animalcule is a long slender line ; another is coiled 
i 5 
\ 
| 
ANIMALCULE.. 
191 
up like an eel, or a serpent; some are circular, 
elliptical, or globular; others present the form of 
a triangle or a cylinder; some resemble thin flat 
plates, and some may be compared to a number 
of articulated reeds; one is like a funnel, an- 
other like a bell; and the structure of many can- 
not be compared to any object familiar to our 
senses. Certain animalcules, such as the Proteus 
difiluens, Plate III., Figs. 1, 2, and 3, can change 
their figure at pleasure; being sometimes ex- 
tended to immoderate length, and then contracted 
to a point. One moment they are inflated into 
a sphere, the next completely flaccid, and then 
various eminences will project from the surface, 
altering them apparently into animals entirely 
different. Neither is the peculiar motion of ani- 
malcules less remarkable. In several species, it 
consists of incessant gyration on the head as a 
centre, or around a particular point as if one of 
the foci of an ellipse. The progression of others 
is by means of leaps or undulations; some swim 
with the velocity of an arrow, the eye can hardly 
follow them; some drag their unwieldy bodies 
along with painful exertion; and others again 
seem to persist in perpetual rest. These obser- 
vations lead to consideration of the inconceivable 
minuteness of the organs, and the component 
parts of these organs, by which such motions are 
performed. 
The food of the different species of animalcules | 
is not yet indisputably ascertained: probably it 
consists both of animal and vegetable matter; | 
and they also prey on each other. The latter cir- 
cumstance, indeed, has been denied; for it is 
maintained by several authors, that, if the vortex 
which many are endowed with the faculty of cre- 
ating in the fluid, does ingulf other animalcules © 
along with vegetable substances, the former are 
rejected and escape in safety. Other authors 
maintain the opposite opinion with equal confi- 
dence. Leeuwenhoek, in speaking of the Wheel 
animal, indicates his belief of this fact. Ellis says 
the same of an animalcule denominated by- him 
Volvox vorax. Goeze has seen the Trichoda cimex 
devour the lesser animalcules voraciously; and 
Spallanzani, speaking of this subject, observes 
that animalcules feed so greedily upon each other 
as to become larger, and prove indolent and slug- 
gish. On the contrary, if reduced to abstinence, 
by being kept in distilled water, they are full of 
spirit, and eagerly devour the minuter animal- 
cules supplied to them ; while the transparency of 
their bodies allows us to perceive their prey, still 
retaining motion after being swallowed. Baron 
Gleichen, in 1781, tinged water with carmine, 
and mixed it with an infusion. On the second 
day, the internal colour of the animalcules showed 
that most of them had swallowed part of the 
liquid. Dr. Ehrenberg, by diffusing pure indigo 
in the water which contained them, was enabled 
by observing the progress of the coloured particles 
through their transparent bodies, to arrive at 
certain conclusions respecting their anatomical 
id 1 
