GASTEROPODA. Te 
“ The shells of the newly-hatched animals have 
been frequently considered as distinct species, and 
some very thin shells of land Mollusca, such as 
Vitrine, have been taken for the young of other well- 
known species, as Helix hortensis. ‘These young 
shells are easily known by their always being of 
a pale horn colour; the whorls are generally rather 
irregular, and enlarge very rapidly; and the apex 
of the whorl, which was first formed, is generally 
large and blunt compared with the size of the shell. 
They are always destitute of colour, for the animal 
does not deposit the colouring matter until after it 
has been hatched; and it is therefore generally 
easy to distinguish, in the young shell, (and some- 
times also in the adult,) that part of the top of the 
spire which formed the shell of the animal when in 
the egg. | 
“The shell is formed by the hardening of the 
animal matter, which is secreted by certain glands 
on the surface of the body, by means of chalky 
matter, which is also secreted by similar glands. 
It has been stated that the unhatched animal, very 
shortly after it is formed, begins to make its shell; 
and when it is hatched, deposits on the edge of the 
mouth of the little shell, which covered its body in 
the ege, a small quantity of the mucous secretion. 
This dries, and is then lined with some mucous 
matter, intermixed with calcareous particles; and 
when this hardens, it again places on its edge an- 
other very thin layer of the mucous secretion, and 
again lines it as before. The mucous secretion 
first deposited forms the outer coat of the shell, and 
is of use in protecting it from injury, while the 
mucous matter mixed with lime, which is placed 
within it, forms the substance of the shell itself. 
