E. NEWTON HARVEY. 



extract, with platinized asbestos and hydrogen. I later discov- 

 ered that Ctenophore extracts will luminesce in complete absence 

 of oxygen 1 and presume that oxygen must be bound in some way 

 with the photogenic granules. It is quite possible, then, that 

 the inhibition by light in Ctenophores may also be due to photo- 

 chemical acceleration of oxidation (without luminescence) of 

 photo-genie material. 



CONCLUSIONS. 



Inhibition of luminescence of photogenic material by light is 

 not a general phenomenon. Ctenophores remain the best known 

 case, but in my experience pennatulids and medusae show no 

 inhibition. Cypridina extracts are also inhibited if they contain 

 oxygen and the inhibition seems to consist of an oxidative 

 destruction of photogenic substance. 



I have never yet observed an animal that would fail to lumi- 

 nesce in the daytime provided it had been kept in darkness for 

 a few hours previously. Flagellates and copepods should be 

 studied further to test the question of day-night rhythm of 

 luminescence. 



REFERENCES. 

 Allman, G. I. 



'62 Proc. Roy. Soc. Edinb., IV., 518. 

 Harvey, E. N. 



'25 Journ. Gen. Physiol., VII., 679. 

 Heinemann, C. 



'72 Arch. f. Mikr. Anat., VIII., 461, and XXVII., 296. 

 Heymans, C., and Moore, A. R. 



'23 Journ. Gen. Phys., VI., 273. 

 Massart, J. 



'93 Bull. sc. de France et de la Belgique, XXV. 

 Moore, A. R. 



'26 Journ. Gen. Physiol., IX., 375. 

 Moore, B. 



'08 Bioc. Journ.. IV., i. 

 Parker, G. H. 



"20 Proc. Amer. Phil. Soc., XIX., 171 

 Zacharias, O. 



'05 Biol. Centralb., XXV., 20. 



1 Not yet published. 



