32 LIVING LIGHTS. 



allies, of casting their arms wlien touclied; so that it is 

 extremely difScult to take them intact. In lifting an Astro- 

 phyton ^ from a branch of coral, we have had it drop into 

 myriads of pieces ; so that there was a mimic rain of arms 

 upon the bottom. This we found could be avoided by mak- 

 ing the transfer under water, and, when the " basket-fish " was 

 safely in the jar, killing it by the introduction of alcohol. 



As to the cause of the light in the star-fishes, little is 

 known. Quatrefages, after a careful examination of an 

 Ophiuran, came to the conclusion that the light emitted 

 was due to muscular contraction; observing it arising be- 

 tween the plates of the arms and not on the disk, where, 

 however, it has been seen since his observations were made. 

 Professor P. Martin Duncan found upon examining a speci- 

 men, brought from the icy sea of North Smith's Sound, by 

 Sir George Nares's expedition, that it had a delicate mucous 

 envelope, which, he thought, in the young covered the plates 

 and bases of the spines. In this filmy covering, he suggests, 

 may be found the seat of the illuminating power. 



