THE PHOSPHORESCENCE OP THE SEA. 
293 
efficacious agency) if a little alcohol be added., the effect be- 
comes very marked. The light of the whole is perceptibly 
increased, and those animalculse whose entire substance shines 
with a steady white light, multiply considerably in numbers. 
This result may be exhibited in a most pleasing manner as 
follows : — a long tube must be filled with water well charged 
with Noctilucae, and a drop or two of sulphuric acid subse- 
quently poured gently into the tube. In its descent this will 
acidulate the water, and will be found to operate as one of the 
most active irritants that can be applied to the animalcule, of 
which it rapidly disorganizes the substance. As, therefore, this 
formidable drop descends, it appears to ignite the Noctilucee in 
its passage, and thus its downward course may readily be 
traced. 
Here, again, is a still more beautiful experiment producing 
similar effects. 
If the lower extremity of a tube, replenished as above, be 
plunged into water raised almost to the boiling point, at the 
moment of its immersion not the least light is visible. 
Soon, however, some scintillations are apparent at the bottom 
of the tube, and as the liquid becomes heated, and the warm 
currents rise from below upwards, the luminous animalcuhe 
multiply in numbers. In a few moments they are all luminous, 
and the tube then presents the appearance of a fiery rod. This 
brilliancy does not, however, last long : the little illuminated bal- 
loons are extinguished one after another, and do not recover 
their luminous properties even if transferred to cold water. 
When I tried the experiment, a temperature of 39° * had killed 
them all. 
But there are no observations connected with the Noctiliicae 
that will compare in beauty and interest with those which may 
be made with the assistance of the microscope. 
In proportion as the magnifying power of the instrument is 
increased, we see reproduced in each animalcule the effect 
that we noticed on approaching the luminous waves of the 
sea-beach. 
Examined with a power of 20 to 30 diameters, the illumi- 
nated portions of the body of Noctilucae present a uniformly 
bright aspect. With 60 diameters a number of small but bril- 
liant scintillations become visible, detaching themselves, as it 
were, from parts of what appears to be a pale luminous back- 
ground and these scintillations come and go Avitli the rapidity 
of lightning. An enlargement of 150 diameters, however, 
reveals the true character of the phenomenon. It then becomes 
obvious that the fight emitted from the whole body, or any of 
its parts, is composed of a vast number of instantaneous scintil- 
* 39° Reaiuner equal to a little less than 120° Fahrenheit, 
x 2 
