48 THE OYSTER. 



the body, of growing and dividing up into cells, which 

 shall shape tliemselves into a new organism like that 

 from whose body the ^^^ came. Most of the steps 

 in this wonderful process may be watched under the 

 microscope, and, owing to the ease with which the 

 eggs of the oyster may be obtained, this is a very 

 good Q^^ to study. 



About fifteen minutes after the eggs are fertilized, 

 Plate IV, Fig. i, they will be found to be covered 

 with male cells. In about an hour the ^^% will be 

 found to have changed its shape and appearance. It 

 is now nearly spherical, and the germinative vesicle is 

 no longer visible. The male cells may or may not 

 still be visible upon the outer surface. In a short 

 time a little transparent point makes its appearance 

 on the surface of the ^%^, increases in size, and soon 

 forms a little, projecting, transparent knob — the polar 

 globule. 



Recent investigations tend to show that while these 

 changes are taking place, one of the male cells pene- 

 trates the protoplasm of the ^%% and unites with the 

 germinative vesicle, which does not disappear, but 

 divides into two parts, one of which is pushed out of 

 the ^^^ and becomes the polar globule, while the 

 other remains behind and becomes the nucleus of the 

 developing ^^%, but changes its appearance so that it 

 is no longer conspicuous. The ^g^ now becomes 

 pear-shaped, with the polar globule at the broad end 

 of the pear, and this end soon divides into two parts, 

 so that the ^g^ is now made of one large mass and 

 two slightly smaller ones, with the polar globule 

 between them. Plate IV, Fig. 2. 



