BY MOLECULAR COALESCENCE. . 9] 
crustaceans to be mentioned is that which corresponds to 
the osseous tendons of birds. It is to be found most deve- 
loped where it is attached to the claws called the nippers. 
There is one attached to all the extreme claws. This part, 
like the preceding, is buried between muscular fibres. 
It consists of fibrous layers partially calcified, applied, toge- 
ther. Its structure is like that of the last part. Thin 
transverse sections through the thickest part exhibit the 
lines and lamelle, as described in the tegumentary portion. 
Frequent reference having been made to the resemblance 
between the form of the carbonate of lime in these shells 
and that in the artificial products, I would wish it to be 
particularly observed, that in comparing these products— 
the artificial with the natural—the parts compared must be 
in the same molecular condition, that is, the molecular, 
the globular, and the laminated of the one, must, be 
severally compared with the corresponding forms of the 
other, as there is but little resemblance in the appearance 
of the different forms of this compound, whether artificial 
or natural, when in different states of molecular arrange- 
ment; but the natural products do not differ in this re- 
spect more from the artificial than the various forms of 
the latter, in their dissimilar molecular conditions, differ 
among themselves; for nothing can be more unlike in 
appearance than the clear spherules, as they exist sepa- 
rately, and the globular bodies which they form by their 
coalescence, when their molecules have undergone their 
final arrangement into lamin and radiating imperfectly 
erystalline fibres, the closest inspection of the one could 
never suggest the idea of their being made up of the other. 
Such being the resemblance of the various parts of the 
shell in this class of animals, with the corresponding forms 
obtained by the artificial process, it now remains to ex- 
