IOO TlMEHRI. 
and, in spite of numerous statements to the contrary by 
numerous observers, the only certain methods of multipli- 
cation known are those which depend on portions of the 
body substance being detached or on the body itself split- 
ting up into two or more pieces, each of which grows to 
the size of the form from which it was developed, and in 
turn repeats the processes of fission. 
Though the Animalcules are destitute of all the various 
complicated systems and tissues which are present in the 
higher animals, and though all their essential features 
of organisation are so extremely simple, yet their vital 
processes of growth and reproduction are performed 
with the utmost degree of perfe6lion ; and the simple 
speck of protoplasm fulfils the various functions of sen- 
sation, muscular a6livity, and nutrition, as adapted to 
the struggle for existence in its surroundings, as com- 
pletely as the complicated apparatus of the highest forms. 
It will thus be understood that though minuteness of 
size is the prominent idea to be conveyed by the term 
Animalcule, yet simplicity of strufture is almost equally 
characteristic, so that the two features may be looked upon 
as correlative. And just as, with regard to organisation, 
there is a marked degree of variation among the different 
kinds of Animalcules, so also, as regards minuteness of 
size, is there the same degree of variation. For while, on 
the one hand, there are forms which are visible to the 
naked eye, some of which indeed attain to a size of more 
than half an inch in diameter, on the other hand, there 
are others which, after being magnified several millions 
of times, are but barely discernible under the micro- 
scope — organisms of such minute dimensions as to make 
it impossible for the mind to pifture them. Between 
