THEORY OF THE CELLS. 207 
crystallization, but which exist in some other unknown manner 
between the atoms of solid substance. It is not possible, 
therefore, to determine whether that part of the crystal which 
is first formed must have an angular figure or not. 
An ordinary crystal consists of a number of lamin; when 
so small as to be but just discernible, it has the form which 
the whole crystal afterwards exhibits, at least as far as regards 
the angles; we must therefore suppose that the first layer is 
formed around a very small corpuscle, which is of the same 
shape as the subsequent crystal. We will call this the pri- 
mitive corpuscle. It is doubtful what may be the shape of 
this corpuscle in the crystals which are capable of imbibition. 
The first layer, then, is formed around the corpuscle in the 
way mentioned; it grows by intussusception, and thus forms a 
hollow, round or oval vesicle, to the inner surface of which the 
primitive corpuscle adheres. As all the new molecules that are 
being deposited may be placed in this layer without any altera- 
tion being required in the law which regulates the coalescence 
of the molecules during crystallization, we must conclude that 
it remains the only layer, and becomes greatly expanded, so as 
to represent all the layers of an ordinary crystal. It is, how- 
ever, a question whether there may not exist some reasons why 
several layers can be formed. We can certainly conceive such 
to be the case. The quantity of the solid substance that must 
crystallize in a given time, depends upon the concentration of 
the fluid; the number of molecules that may, im accordance with 
the law already mentioned, be deposited in the layer in a given 
time depends upon the quantity of the solution which can 
penetrate the membrane by imbibition during that time. If 
in consequence of the concentration of the fluid there must be 
more precipitated in the time than can penetrate the mem- 
brane, it can only be deposited as a new layer on the outer 
surface of the vesicle. When this second layer is formed, the 
new molecules are deposited in it, and it rapidly becomes ex- 
panded into a vesicle, on the inner surface of which the first 
vesicle lies with its primitive corpuscle. The first vesicle now 
either does not grow at all, or at any rate much more slowly, 
and then only when the endosmosis into the cavity of the 
second vesicle proceeds so rapidly that all that might be pre- 
cipitated while passing through it, is not deposited. The second 
