A PHYSIOLOGICAL STUDY OF SPECIFIC GRAVITY AND OF 



LUMINESCENCE IN NOCTILUCA, WITH SPECIAL 



REFERENCE TO ANESTHESIA. 



By Ethel Browne Harvey. 



INTRODUCTION. 



The present study has been chiefly concerned with the specific 

 gravity and the effects of anesthetics on the luminescence of Noctiluca. 

 The effects of other substances— acids, alkahes, KCN, etc. — have also 

 been studied, as well as the action of electricity, change of osmotic 

 pressure, temperature, etc., in order to gain an accurate knowledge of 

 the more general physiological aspects of luminescence in this form. 

 Some observations on these subjects were made by Quatrefages in 1850, 

 Krukenberg in 1887, and Massart in 1893, but most of the work is too 

 old and the methods too crude to be of much value, since definite con- 

 centrations were not considered nor the results interpreted from the 

 physico-chemical aspect. 



The results were obtained at the Marine Biological Laboratory of 

 the Imperial University of Tokyo, situated at Misaki, Japan, where 

 the great abundance of Noctiluca offered unusual advantages. The 

 animals occur in such quantities that a layer an inch thick on the 

 surface of a large aquarium jar can soon be collected, and on dark 

 nights the sea is extremely brilliant in any area where it is disturbed, 

 especially where the waves lap the shore. It gives me pleasure to thank 

 Professor I. Ijima for the facihties of the laboratory, and also Pro- 

 fessor C. Ishikawa for his many kindnesses during my stay there. 



LIGHT RESPONSE IN NOCTILUCA. 



As is well known, noctilucas, when undisturbed and under perfectly 

 normal conditions, are not luminous; but when disturbed or stimulated 

 in any way, they give a bright flash of a distinctly bluish tinge, lasting 

 only an instant. This is the normal hght-response of Noctiluca. If, 

 however, the animals are not in good condition, a faint, continuous 

 glow issues from them; such a glow is usually preluninary to the death 

 of the animals, and is also cafled forth by many experimental condi- 

 tions. These two are the only light responses of the animals. There 

 is never, under normal conditions, a rhythmic flashing, such as is 

 characteristic of certain species of firefly, nor is it possible, by any 

 chemical or physical means, to call forth a rhythmic flashing compa- 

 rable with the rhythmic twitching of a muscle in pure NaCl. 



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