39. Observations on the Luminosity of some Animals 
in the Gangetic Delta. 
By B. Prasuap, D.Sc., Zoological Survey of India, Calcutta. 
(Published by permission of the Director, Zoological Survey 
of India.) 
River in the Gangetic Delta,” in which he had recorded some 
in their favour, that the observations were made on arge 
numbers of individuals and that the investigations were carried 
out at practically all hours of the day and night and at differ- 
ent times of the year. 
Before going on to the subject proper it may be noted 
that the Fauna of the various streamlets and creeks in the delta 
resembles that of the Matlah river, in that it is very rich in 
individuals though very poor in the number of species repre- 
sented. This was fortunate for the investigation, as the circle 
of work was greatly narrowed and I was able to pay greater 
attention to the few species with which I had to deal. In 
the case of most of these also my results were negative, but 
in the case of four:—1l. Harpodon nehereus (Ham. Buch.)—a 
fish, 2. Leander tenuipes, Henderson—a prawn, 3. a race of 
Pleurobrachia globosa and 4. Beroe cucumis, Fér.—two rove 
phores, I was able to observe the production of light. me ; 
methods of the production of ae hye different in differen 
cases I will deal with each separately. ; 
The interesting fish known to the scientists as oes 
nehereus and popularly known as the ‘‘ Bombay srs ie in 
‘ Bummalok”’ is fairly common in the lower reaches ie ee 
delta. This species along with the only other species of t 

ee tk a SO Oe a era: 166 (1000 
