120 



EMISSION OF LIGHT 



salia, Salpa, certain Nereids; and among the Star- 

 fish (Asterias), I should mention the Ophiura, or 

 Sand-stars. 



Fig. 21, 



Medusce (figs. 19, 20, 21, and 22) and Cyaneas 

 possess this luminous property to a very high de- 



