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 of Veretilla and Virgularia (Sea Rush) are 
known to be self-luminous. The thick branchy 
Aleyonidium gelatinosum (fig. 23), which is only 
found attached to rocks situated in deep water, 
