172 THE NORTHERN MICROSCOPIST. 

permit me to glance at two or three of the lowliest life-histories in 
nature, to see whether they—where we know them well—indicate 
uncertainty or suggest caprice. 
I begin with one of the simplest and lowest algee known in 
Nature, Protococcus pluvialis, and I deal with it in its simplest con- 
dition, z.¢., the resting and the motile states of the green unicellular 
plant. 
The history I give has been long known, and has been confirmed 
by many, but the drawings I give have been verified from nature, 
and the objects are magnified 1,000 diameters. 
The whole plant is a microscopic globule. In its “still” con- 
dition it is a delicate globe, transparent, but filled with a reddish 
yellow granular mass ; if not seen to be at first constricted cen- 
trally, it quickly becomes so, as in Fig. 2 a, and each part contains 
a nucleus, as the drawing shows. It soon increases in size, as in 
6, the nuclei enlarging and the area of the envelope becoming 
much extended; at this time the colour of the granular mass 
changes into greenish, and then distinctly green; but the nuclei 
becomes almost colourless. Cross division now ensues, as in ¢, 
which may go on until sixteen or more cells are seen to be formed 
within the hyaline envelope. Soon the cells separate and fine vibra- 
tile lashes or flagella show themselves (shown for the sake of clear- 
ness only in two instances in Fig. 2 @). The envelope now opens, 
and these flagellate globules go free ; but a nucleus manifests itself, 
as is seen in é, which is shortly seen to be undergoing constriction, 
as atf This speedily divides into two, as in g, then the flagella 
falls off, the hyaline envelape becomes more manifest, the little 
organism is perfectly at rest, and soon assumes the condition seen 
at a. with which the cycle begins again. 
Observe, then, that although this process is so simple as to be 
immeasurably below those that’ come immediately above it, there 
is no caprice, no unformulated phoenomena, and yet this may be 
observed for weeks, or even months together. 
Only clearly remember, this is the observed phcenomena in the 
living and normal plant. Let, however, a mass of dead protococci. 
accumulate in trough or live-box, mingled with living ones, and all 
the complex issues of decomposition immediately arise. 
Proceed now a step higher. We are still with the lowly alge, 
and I select a Desmid. With the group you are mostly, doubtless, 
familiar. They are minute but elegant plants, consisting of isolated 
cells, which live in every pond, ditch and streamlet on the surface 
of the earth. They are exquisitely minute, with delicate grace of 
form and beauty of colour. They are amongst the lowliest of 
living things. How do they multiply? and in the life-history of 
these delicate cells is there irregularity, uncertainty, or caprice? 
No; there is no discoverable departure from the secular process 
