18 FORMATION OF SHELLS OF ANIMALS, ETC., 
describe a curve, whose elements might probably be de- 
termined by a due consideration of the conditions of its 
motion. As the principal object of this paper is physiolo- 
gical, this is a task which it would be foreign to my purpose 
to attempt. It will now be obvious, from what has been 
stated respecting the change of position of the molecules 
of two spheres in the course of their coalescence into one, 
that, in a calculus made up of a conglomeration of sphe- 
rules, the molecules of each spherule, having been pre- 
viously arranged in reference to its own centre, will have 
to leave their former positions, and pass over a certain 
space before they gan gain their final positions in the 
sphere of which they are to form a part. Hence, prior to 
the complete coalescence of any number of spherical par- 
ticles into one sphere, each particle or spherule must 
undergo a process of disintegration (or be taken to pieces), 
and after that, the molecules of the disintegrated spherules 
must be put together again under the same static condi- 
tions as they were before. These processes are not of 
course performed at separate periods, so that after one is 
completed the other begins; but they may both be going 
on at the same time in different parts of the same 
sphere. Now, the question may be raised whether 
these processes are so thoroughly molecular as is here 
inferred; that is, whether they extend to the actual 
separation and re-arrangement of ultimate molecules 
or atoms, or whether it is not sufficient that the com- 
ponent spherules should be reduced only to extremely 
small pieces, and these packed closely together m the 
resultant spheres? As, according to this supposition, the 
sclid which would result from the coalescence of these 
imaginary small pieces would be a polygon, with a more 
or less regular contour, and as the effect of gravity upon 
