64 THE MICROSCOPICAL NEWS. 
manner as other algze by the elongation and division of the cells ; 
but we must remember that the diatoms, as we usually see them 
mounted, are the ends or septe, and that it is the side or hoop 
which connects these, that elongates. What interests us most at 
present is the fact that in building up these cells the protoplasm 
has not only to obtain from the surrounding water the materials 
requisite for an increased quantity of endochrome, but also the 
silex or flint for the cells or boxes as we have called them. But, 
inasmuch as these diatoms have a cell wall in which the deposition 
of silex takes place, the curiosity of their production is much 
exceeded by that of the polycistina in which this is absent, and 
which, it seems to me, is one of the most striking examples we 
have of the kind of constructive power of protoplasm we are now 
considering. You are doubtless all acquainted with their beautiful 
forms either from observation, or from illustrations you have 
seen, not forgetting those finished ones shown last year by our 
good friend (Mr. Williams) in illustration of his interesting paper 
on Silex. These shells, as we may call them, are very minute, 
with comparatively large perforations, giving them a reticulated 
appearance, and many of them have solid silicious prolongations 
symmetrical, and curved angular or branched. In some cases 
there is one silicious shell within another, with these prolongations 
originating in the inner one, and passing through both. They are 
very widely distributed, having been found on nearly every ocean 
floor. They are also found in thick deposits of the last geological 
periods. Now these shells are tenanted by specks of protoplasm 
which have constructed them, extracting the necessary silex from 
the surrounding water, and when we remember the infinitesimally 
small quantity of silex which water can hold in solution we may 
form some faint idea of the wonderful nature of the process. It is 
very different from the construction of ordinary shells, which to a 
considerable extent represent the shape of their occupants ; for 
here we have shapeless specks of protoplasm building up of most 
refractory material structures of the most varied forms, but always 
symmetrical and beautiful—another instance of what unorganised 
protoplasm can do. ‘There are several other powers of protoplasm 
well worthy of notice, but I will content myself with referring to 
only one of them, that one however being, perhaps, more wonder- 
ful and incomprehensible than all the others, and, therefore, more 
interesting, and that is the power of transmitting individual 
properties, characteristics, and peculiarties from one generation to 
another; a power which is exercised through the whole animal 
and vegetable kingdoms from the lowest to the highest forms, and 
upon which rests the universal law that like produces like. The 
amoeba wanders about appropriating and assimilating pabulum until 
it attains a certain size, or rather an uncertain one, as they attain 
