96 E. NEWTON HARVEY. 



the surface of certain plates and possess ducts that empty through 

 pores in the cuticula, but not enough secretion is passed to the 

 outside to give a luminous solution. The whole animals stimu- 

 lated electrically in sea water plus platinized asbestos and air 

 give a bright luminescence but no luminescence when stimulated 

 in sea water plus platinized asbestos through which hydrogen 

 has been passed for some time. 



Balanoglossus minutus. The whole of the skin produces a 

 luminescent slime whose light does not last very long. If the 

 whole animal is shaken in sea water through which pure H 2 is 

 passing, there is no luminescence but on admitting air both worm 

 and sea water show luminescence. 



Copepods. (Several species.) The cells are unicellular glands 

 in definite positions in the body or in the legs, secreting to the 

 exterior. When heated slowly in sea water with air the copepods 

 give a bright luminescence but when heated slowly in sea water 

 and platinized asbestos through which hydrogen was passed 

 there was no luminescence. In one experiment the temperature 

 was raised to boiling in the hydrogen atmosphere, then cooled 

 and air admitted. The solution became faintly luminescent. A 

 small amount of oxygen will cause luminescence and the hydrogen 

 must be passed for some time to obtain anaerobic conditions. 



Heteroteuthis dispar. A squid in which a secretion from a 

 gland (part of ink sac) is shot into the sea water as a bluish 

 luminescent cloud of small granules often sticking together in 

 clumps and filaments. On a microscope slide tinder a cover 

 slip the secretion luminesces only at the edges in contact with 

 air (but luminesces uniformly when the cover slip is lifted). 

 When hydrosulphide is added to the secretion in a test tube the 

 luminescence disappears except at surface but returns on shaking 

 with air. Oxygen is necessary for luminescence. 



Quatrefages observed luminescence of Noctilnca under what he 

 regarded as anaerobic conditions whereas E. B. Harvey (1917) 

 found the luminescence of Noctiluca to become very faint in a 

 current of impure hydrogen (made in a Kipp generator but last 

 traces of oxygen not removed) but to regain its brightness when 

 air was admitted. It would seem that Noctiluca must require 

 oxygen for luminescence. In view of my experiments with 



