758 
MICROSCOPIC ANIMALS. 
they move and take an opposite one ; and by inclining the glass on 
which the drop of water is, as it can be made to move in any direc- 
tion, so the animalcules appear to move as easily against the stream 
as with it. When the water begins to evaporate, they flock towards 
the place where the fluid is, and shew a great anxiety and uncommon 
agitation of the organs with w'hich they draw in the water. These 
motions grow languid as the water fails, and at last cease altogether, 
without a possibility of renewal, if they be left dry for a short time. 
They sustain a great degree of cold, as well as insects, and will perish 
in much the same degree of heat that destroys insects. Some ani- 
malcules are produced in water at the freezing point, and some insects 
live in snow. By mixing the least drop of wine with the w'ater in 
which they swim, they instantly fall into convulsions and die. The 
same rule seems to hold good in those minute creatures, which is 
observable in the larger animals, viz. that the larger kinds are less 
numerous than such as are smaller, while the smallest of all are found 
in such multitudes, that there seem to be myriads for one of the 
others. They increase in size like other animals, from their birth 
until they have attained their full growth ; and when deprived of pro- 
per nourishment, they in like manner grow thin and perish.’^ 
The modes of propagation among these animalcules are various, 
and the observation of them is extremely curious. Some multiply 
by a transverse division ; and it is remarkable, that though in general 
they avoid one another, it is not uncommon, when one is nearly divi- 
ded, to see another push itself in upon the small neck which joins 
the two bodies, in order to accelerate the separation. Others, when 
about to multiply, fix themselves to the bottom of the water ; then 
becoming first oblong, and afterwards round, turn rapidly as on a cen- 
tre, but perpetually varying the direction of their rotary motion. In 
a little time, two lines forming across are perceived ; after which 
the spherule divides into four, which grow, and are again divided 
as before. A third kind multiply by a longitudinal division, which in 
some begins in the fore part, in others in the hind part ; and from 
others a small fragment detaches itself, which in a short time assumes 
the shape of the parent animalcule. Lastly, others propagate in the 
same manner as the more perfect animals. 
Some doubts have arisen whether those minute bodies really do 
en joy animal life ; or whether they are not in many cases to be account- 
ed only inanimate and exceedingly minute points of matter, actuated 
by the internal motion of the fluid. But to all, hypotheses of this 
hind, Mr. Adams makes the following reply. “ From what has been 
said it clearly appears, that their motions are not purely mechanical, 
but are produced by an internal spontaneous principle ; and that they 
must therefore be placed among the class of living animals, for they 
possess the strongest marks of the most decided characters of anima- 
tion ; and consequently, that there is no foundation for the supposi- 
tion of a chaotic and neutral kingdom, which can only have derived 
its origin from very transient and superficial views of these animal- 
cules.-' 
