525 



THE MICROSCOPE 



destined for the egress of the polypides. The tentacula 

 are about sixty in number, long, and ciliated on either 

 side. The statoblasts are ovoid, of a dark-brown colour 

 without marginal spines, and contained within the poly- 



Fig. 247. 



1, Portion of a transverse section of the spine of an Echinus. 2, Crystals of 

 carbonate of Lime, from the surface of shell of Oyster. 3, Horizontal section 

 of shell of Haliotis splendens, with stellate pigment in the interior. 4, 

 Portion of shell of a Crab, showing granules beneath the articular layer, 5, 

 Another portion of the same shell, showing its hexagonal structure. 



pidom, through the transparent walls of which they can be 

 readily seen. It occurs in greatest perfection during the 



