FOSSIL POLYCYSTINA 83 



objects by throwing a light through them from below. 

 Others mount them in fluid glycerine, so that they 

 are free to move about. Viewed transparently, as in 

 this last method, when the polycystina roll down 

 they appear to take the opposite direction, and 

 the effect is charming. They roll over and over, and 

 display every portion of their symmetrical outlines, 

 many of them showing the inner concentric perforated 

 balls which resemble the ivory ones to which we have 

 referred. The pattern is not, however, limited to the 

 ball series, for we find cups, and helmets, and bowls, 

 and mitres, in endless succession. Whether it be 

 viewed under the microscope, or in a greatly enlarged 

 form, as on the lantern screen, a slide of polycystina 

 always creates profound admiration. 



The fossilized varieties, as we have seen, are doubly 

 hidden, in that they enter into the composition of 

 certain rocks, and when separated are so small that a 

 good microscope is required to render them individu- 

 ally visible. Although labouring under the great 

 disadvantage of being lifeless for, long ages ago, 

 they were deprived of their exquisitely beautiful 

 tenants, and now consist only of the flinty, forsaken 

 homes yet they are so wonderful and so attractive 

 that, view them as often as we may, we can never tire 

 of them. We are always ready to see them again, 

 and we put them in the foreground at all meetings 

 where the public is invited to see wonders revealed 

 by the microscope. We must be careful not to 

 confuse the polycystina with the homes of other 



