THE OVAEIAN EGG. 277 



the beach, soon 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 consolidated, 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 



