e 
THE- OVARIAN EGG. 277 
the mo covers itself with sand, the par- 
ticles of which, in contact with the glutinous 
substance of the eggs, quickly form a cement 
that binds the whole together in a kind of paste. 
When congplidated, it drops off from the shell, 
having taken the mould of its form, as it were, 
and retaining the curve which distinguishes the 
outline of the Natica. Although these saucers 
look perfectly round, it will be found that the 
edges are not soldered together, but are simply 
lapped one over the other. Every. one of the 
‘thousand little spheres crowded into such a circle 
of sand contains an egg. If we follow the develop- 
ment of these eggs, we shall presently find that 
each one divides into two halves, these again 
dividing to make four portions, then the four 
breaking up into eight, and so on, till we may 
have, the yolks divided into no less than sixteen 
distinct parts. Thus far this process of segmen- 
tation is similar to that of the egg in other ani- 
mals; but, as we shall see hereafter; the regular 
segmentation of an egg seems usually to re- 
sult only in a change in the quality of its sub- 
‘stance, for the portions coalesce again to form 
one mass, from which a new individual is finally 
sketched out, as a simple embryo at first, but 
gradually undergoing all the changes peculiar 
to its kind, till a new-born animal escapes from 
the egg. In the case of the Natica, however, this 
