BY INFERIOR ORGANISMS. 



121 



gree, and so do many polypes, such, as the Penna- 

 tula, known to naturalists as the Phosphorescent 

 Sea-pen, and in French as Plumes de mer. Some 



Fig. 22. 



species ofVeretilla and Virgularia (Sea Rush) are 

 known to be self-luminous. The thick branchy 



Fig. 23. 



Alcyonid'ium gelatinosum (fig. 23), which is only 

 found attached to rocks situated in deep water, 



