I. ROBINSON—THE DIATOMACEJE. 
5 
we shall perhaps obtain a better idea of the result if we consider 
what the superficial amplification amounts to. This in the case of 
the half-inch objective would amount to about 82,000 times, and 
with the i\th inch to upwards of 560,000. Let us for a moment 
imagine it possible to subject one of our own species to such an 
amplification as is represented by these powers. Take, for example, 
a man 6 feet in height. TJnder the lower scale of amplification 
he would acquire an apparent stature of upwards of 1000 feet r and 
under the higher power one of 4,500 feet, or a greater elevation 
than the highest mountains in Britain. 
These powers are, however, by no means excessive for the effi¬ 
cient study of the forms and marking of the Diatomacese. I have, 
indeed, sometimes subjected them to a far higher degree of magni¬ 
fication, having obtained a linear amplification of about 5000 
diameters, or a superficial enlargement of about 25 millions of 
times. But, to whatever extent this process is carried, no trace 
of imperfect workmanship can be discovered, the minutest detail 
being invariably found to be executed with unerring exactness and 
precision. 
The power of spontaneous motion possessed by the free forms 
has already been referred to. This motion is of a peculiar character. 
In many cases it consists of a series of jerks, and after a short space 
has been traversed the path is usually retraced. It has a pecu¬ 
liarly undecided and aimless appearance, and reminds one of the 
uncertain steps of a man suffering from the evil effects of “ the 
sweet poison of misused wine.” It seems to be of a purely 
mechanical character, and there is no trace of the power of self- 
direction which is usually possessed by animal natures. The 
means by which it is accomplished are also unknown to us, and 
remain an unsolved enigma to the present hour, for the microscope 
with all its wonderful revelations has not yet disclosed them. 
We pass on now to a brief consideration of the mode of repro¬ 
duction amongst the Diatomacese, and to that marvellously rapid 
increase in numbers which characterizes them. The usual manner 
in which this is accomplished is by the process termed self-division, 
a mode of increase which takes place amongst many other organisms. 
By this process one single cell becomes two cells exactly similar to 
and as perfect as the original one. These two cells again divide, 
and so the increase of numbers proceeds with a constantly aug¬ 
menting rapidity. The exact time occupied by this' act of self¬ 
division is not known, but Professor Smith supposes it may be 
accomplished in 24 hours. Should such be the case, he calculates 
that the progeny of a single diatom would in one month amount to 
one thousand millions. This process cannot,, however, be regarded 
as a true generic reproduction, but rather as one of gemmation, 
and analogous to the growth of a tree leaf by leaf. Neither does 
it appear that it can be continued indefinitely. After a time the 
requisite energy becomes exhausted, and an altogether different 
process supervenes, resulting in the formation of what are termed 
sporangia, and in the origin of a new generation. The circumstances 
