174 Papers from the Department of Marine Biology. 



stances are concerned in light-production, but Dubois (9) pointed out 

 that in the elaterid beetles and in the mollusc Pholas dactylus such was 

 the case and he showed that these substances could be separated by 

 heat. I can confirm this statement for certain other forms (lampyrid 

 beetles and Cypridina) , but find that the substances in Cypridina have 

 many characteristics different from those described by Dubois for 

 Pholas and that the mechanism of light-production is quite different 

 from that which Dubois (10) supposes.^ A record of the experiments 

 and a discussion of the chemistry of light-production in all its aspects 

 will be found in the following pages. Cypridina, as the most favor- 

 able species, will be considered first and then the other forms which I 

 have studied— the luminous beetles, the pennatulid Cavernularia, lum- 

 inous bacteria, the squid Watasenia scintillans, and a fish (Monocentris 

 japonica) — together with a consideration of certain chemiluminescent 

 reactions which involve the taking up of oxygen. 



Most of the studies reported herein were made in Japan, a region 

 unusually rich in luminous forms, through the kindness of Dr. Alfred G. 

 Mayer and under the auspices of the Department of Marine Biology 

 of the Carnegie Institution of Washington. 



The success of my investigations was largely due to the interest and 

 kindness of Professor C. Ishikawa, of the Zoology Department, Agri- 

 cultural College, Imperial University of Tokyo, and to Professor I. 

 Ijima, of the Imperial University, who extended to me the hospitality 

 of the marine biological laboratory at Misaki. I am also indebted to 

 Dean Kozai and Professor Aso, of the Agricultural College, for the use 

 of many chemicals and apparatus. I extend my cordial thanks to all 

 of these men. 



STUDIES ON THE OSTRACOD CRUSTACEAN C. HILGENDORFII. 

 GENERAL CHARACTER OF LIGHT AND OF LUMINOUS GLANDS. 



Cypridina hilgendorjii is a strongly negatively heliotropic ostracod 

 best obtained at night by lowering into the water fish heads, on 

 which the animals feed. It may be caught the year round, but is 

 most abundant during August and September in Sagami Bay, Japan. 

 Another non-luminous species {Cypridina x.) is often obtained from the 

 fish heads together with C hilgendorjii. It is positively heliotropic to 

 lamplight. C. hilgendorfii is so strongly negatively heliotropic that it 

 is not readily caught on moonlight nights and avoids a shore with many 

 electric lights. 



The light-giving material of Cypridina is a secretion formed in a 

 special gland of yellow spindle-shaped cells, opening near the mouth. ^ 



'All of Dubois's papers are listed in Ann. d. la Soc. Linn, de Lyon for 1913. A general 

 account is given in "La Vie et la Lumiere" Alcan, Paris. 



^For a description of the anatomy of the organ see a paper by N. Yatsu in Journ. Morph., 1917, 

 and Dahlgren (19). 



