BY MOLECULAR COALESCENCE. 93 
mena, until a more advanced state of physiological and 
physical science reveals the chemical, or more probably 
the galvanic, apparatus by which it is produced. But at 
present the fact is all that is necessary to be considered in 
this mvestigation. And in the second place, that as these 
animals live very much in a fluid containing various salts 
of lime in solution, and as their shells are in all parts 
porous, and in some traversed by passages extending from 
the deep to the superficial surface, it seems impossible, 
under such physical and chemical conditions, that these 
two solutions, one containing salts of lime, the other alka- 
line, carbonate, and animal matter, should not first pene- 
trate, agreeably to the law of endosmose, the tissue of the 
shell, and then diffuse themselves, in consequence of their 
unequal densities, through its substance, and lastly, meet- 
ing together, undergo the same chemical decompositions 
with the same results as in the artificial process. If, 
under such physical and chemical conditions, these effects 
are not produced, then laws, which under similar circum- 
stances are invariably operative, must here be suspended. 
But in the present instance exactly the same form of car- 
bonate of lime is produced as ,by the artificial process, 
which is the best evidence possible in favour of the pro- 
cess in the two cases being also the same. Now, with 
this fact, and considering that the same conditions, both 
physical and chemical, have been shown to exist in the 
shell-process as in the artificial one, the evidence in favour 
of the identity of the two processes—the natural and arti- 
ficial—is conclusive. But, notwithstanding all that has been 
said, it is possible that this explanation may be objected to 
by some as being too mechanical to be true. The cell- 
germ hypothesis requiring that all this should be regarded 
as the operation of the vital principle; that the globular 
