94 FORMATION OF SHELLS OF ANIMALS, ETC, 
portions of carbonate of lime of different sizes should be 
looked upon as cell-nuclei and “cells having an organic 
basis essentially cellular, within the cells of which imor- 
ganic matter is secreted and deposited ;” that their curvi- 
linear contour should be regarded as the effect of a vital 
force, and the coalescence of two globules into one as evi- 
dence of cell multiplication by division. Now, in meeting 
this objection, I may observe, that if the globular portions 
of carbonate of lime occurring in these shells, so much 
like the artificial globules as to be deficient in no point 
denoting identity of structure, are the effect of a vital 
force, I see no reason for questioning the identity of the 
vital and physical forces, since, in this case at least, their 
effects upon matter appear in all respects the same. 
Furthermore, as it has been shown that these shells are 
porous and partly membranous, and that the globules of 
carbonate exist in various parts of their substance, and 
that there is also an alkaline solution in contact with the 
deep surface of the shell—indeed, that there exist, either 
within its tissue or contiguous to it, all the conditions ne- 
cessary for endosmose, diffusion, and chemical decompo- 
sition, it must follow, as a natural consequence, that, if 
these globules are not formed on physical principles, but 
by the vital force, the first act of this force will be to put 
a check upon all these physical agencies. To prevent 
chemical action, the external surface of the shell must not 
be penetrated by the water containing one of the elements 
of the globular carbonate of lime, nor the internal or deep 
surface by the fluid furnished by the animal containing its 
other elements, notwithstanding the existence of tubes ex- 
tending from the one surface to the other has been demon- 
strated. And if these solutions should come into contaet— 
and with such mechanical contrivances, apparently in 
