134 FORMATION OF SHELLS OF ANIMALS, ETC., 
nized bodies. This view has certainly the sanction of expe- 
rience. As respects the fact of coalescence in soft structures 
I may observe, that the proofs cannot be expected to be so 
demonstrable as in hard ones, in consequence of the pro- 
cess being in the latter sufficiently slow and gradual to afford 
ample opportunities of observing it through all its stages, 
whilst in the former it would take place too suddenly to 
admit of being observed in detail, one part of the process 
following so closely upon the other as to be distinguishable 
only as one physical act; consequently, im the case of 
coalescence of the softer tissues, other evidence besides 
that furnished by microscopical examination must be 
resorted to. Hence, I may observe that the words hard 
and soft are merely relative terms, implying different 
degrees of cohesion ; and therefore, as it cannot be sup- 
posed that the physical forces acting upon the particles of 
the harder substance, and leading to their coalescence, can 
be different, or can act differently upon the particles of 
the softer ones, leading precisely to the same result, 
(namely, in both cases to the like incorporation of smaller 
particles into larger ones,) the process of coalescence in 
both substances must be identical. I may notice also, m 
reference to the appearances presented by growing car- 
tilage—this being a structure in which development by 
self-multiplication of its cells is considered to be well 
marked—that if an isolated piece of cartilage in this state 
were examined with the microscope, by the side of 
some coalescing globules of carbonate of lime, it would be 
Just as difficult, in the one case as in the other, to say, 
from mere inspection, whether the larger rounded particles 
are the result of coalescence, or of cell-multiplication by 
division. However, if the slide containing the globules of 
carbonate of lime be so moved that the smaller globules 
