202 ACTINOZOA. 



" Glass-plants," whose siliceous stem may be the 

 product, not of the polype-mass, but of the sponge 

 on which it is parasitic. 



Fig. 35. 



ZoANTHAKiA SCLEROBASICA : — Part of a living stem of Anti- 

 •patlies avguina, of the natural size. Two polypes are shown 

 separately, magnified. 



Of the Madrepores, or Z, Sclerodermata, want 

 of space forbids us to say much. A short sketch 

 of the several families into which the sub-order is 

 divided appears to be the best form into which 

 this part of our subject may be condensed. 



Among the Turbinolidoe the coral lum is usually 

 simple, never presenting a coenenchyma. In 

 Coenocyathus continuous lateral gemmation takes 

 place, the corallites so formed remaining con- 

 nected in a close irregular tuft. In Blastotrochus 

 gemmation also occurs, but here it is discon- 

 tinuous. The septa are very perfectly developed, 

 not giving rise to either dissepiments or synap- 

 ticulse {fig. 36 a). 



In the Oculinidce there is a very abundant 

 coenenchyma, which blends gradually with the 



