208 THEORY OF THE CELLS. 
vesicle, when it is developed at all, must needs be developed 
relatively with more rapidity than the first; for as the solution 
is in the most concentrated state at the beginning, the necessity 
for the formation of a second layer then occurs sooner ; but 
when it is formed, the concentration of the fluid is diminished, 
and this necessity occurs either later or not at all. It is pos- 
sible, however, that even a third, or fourth, and more, may be 
formed ; but the outermost layer must always be relatively the 
most vigorously developed ; for when the concentration of the 
solution is only so strong, that all that must be deposited in a 
certain time, can be deposited in the outermost layer, it is all 
applied to the increase of this layer. 
Such, then, would be the phenomena under which substances 
capable of imbibition would probably crystallize, if they did so 
at all. I say probably, for our incomplete knowledge of crys- 
tallization and the faculty of imbibition, does not as yet admit 
of our saying anything positively @ priori. It is, however, 
obvious that these are the principal phenomena attending the 
formation of cells. They consist always of substance capable 
of imbibition ; the first part formed is a small corpuscle, not 
angular (nucleolus), around this a lamina is deposited (nucleus), 
which advances rapidly in its growth, until a second lamina 
(cell) is formed around it. This second now grows more quickly 
and expands into a vesicle, as indeed often happens with the 
first layer. In some rarer instances only one layer is formed ; 
in others, again, there are three. The only other difference in 
the formation of cells is, that the separate layers do not con- 
sist of the same chemical substance, while a common crystal 
is always composed of one material. In instituting a com- 
parison, therefore, between the formation of cells and crystal- 
lization, the above-mentioned differences in form, structure, 
and mode of growth fall altogether to the ground. If crystals 
were formed from the same substance as cells, they would pro- 
bably, in ¢hese respects, be subject to the same conditions as 
the cells. Meanwhile the metabolic phenomena, which are 
entirely absent in crystals, still indicate essential distinctions. 
Should this important difference between the mode of for- 
mation of cells and crystals lead us to deny all intimate con- 
nexion of the two processes, the comparison of the two may 
serve at least to give a clear representation of the cell-life. 
