oe 
ANIMAL LUMINOUSNESS. 
hie yet there was not one on board who 
id not feel some degree of them; and all im- 
puted them to the effect of the light proceeding 
from the surface of the ocean. Mr. Henderson 
remarks; “ For my own part, the headach, &c. 
which followed immediately my looking at the 
water, was particularly severe, nor did it go off 
until morning. The effects I experienced were 
like those produced by smoking too much 
tobacco.”* 
There have been recorded some accounts of 
very intense light produced over a great extent 
of the ocean’s surface by luminous animals, but 
it does not appear that any other voyagers have 
experienced physical effects from the light such 
as are described by Mr. Henderson. The great 
intensity with which it is occasionally produced 
by marine animals, however, is well illustrated 
by the descriptions that are given of the moral 
emotions with which it inspires the beholders. 
Witness, for instance, Mr. Bonnycastle’s descrip- 
tion of a scene which he met with in the Gulf 
of St. Lawrence, (7th Sept. 1826.) While it 
was very dark, a brilliant light, like that of the 
Aurora, was seen to shoot suddenly from the sea, 
in a particular quarter. It spread thence over 
the whole surface of the water between the two 
shores of the Gulf; and shortly there was pre- 
sented “one blazing sheet of awful and most 
brilliant light.” << Long tortuous lines of light 
showed many large fishes darting about as if in 
consternation at the scene.” ‘The light was suf- 
ficient to enable one to see the most minute 
objects on the ship’s deck. On drawing upa 
bucketful of the water, and stirring it with the 
hand, it presented “ one mass of light, not in 
sparkles as usual, but in actual coruscations.”+ 
Messrs. Quoy and Gaimard state that in 
handling luminous marine animals while alive, 
they have always been sensible of an odour pro- 
ceeding from them similar to that which is per- 
ceived around a highly charged electrical appa- 
Tatus. © 
The only observation with which we are ac- 
quainted that seems to indicate the evolution of 
heat in connexion with the light of animals, is 
that reported by Macartney, who states that he 
found the thermometer raised by two or three 
degrees when placed in contact with a group of 
living glow-worms shining, or even with their 
light-giving sacs cut off. The repetition of this 
experiment, however, has not produced the 
-Same result in the hands of others: they saw no 
rise of the thermometer. 
TIT. Circumstances in which light is given 
out, and by which its intensity is affected — 
It is not known whether there be any lumi- 
nous animals that give out light in all circum- 
Stances, and at every period of their existence, 
in their natural situations. So far as observa- 
tion extends, certain mollusca, and some of the 
Species of elater appear to shine without inter- 
mission. But most of the other light-giving 
animals with which we are acquainted use their 
ag function only occasionally, and that, 
or the most part, under some kind of excite- 
Ment or irritation, natural or artificial. In the 
* Trans. Med. and Phys. Soc. of Calcutta, i. 107. 
+ Trans. of Lit. and Hist. Soc. of Quebec, 
199 
absence of more direct means of investigation, 
we may, perhaps, attain to some measure of 
acquaintance with the nature and analogies of 
animal light by inquiring into those sources of 
irritation under which it is given out. Here, 
however, we are met by the difficulty of finding 
contradictory statements of facts made by dif- 
ferent observers. So that our exact knowledge 
on the subject is still insufficient to admit 
of any satisfactory conclusions being drawn. 
What is known on this point may be conveni- 
ently considered under the two following heads. 
I. Circumstances essentially connected with 
the state of nature in which the animals are 
placed when they give out light. 
II. Circumstances artificially produced af- 
fecting the emission of light. 
I. Natural circumstances in which light is 
emitted by living animals. The luminousness 
of animals in their natural state is affected by, 
1. Changes in the state of the medium in 
which they live, whether air or water, in regard 
to its temperature and electricity. 2. By solar 
light. 3. By abrupt collision with other bodies. 
4. By loud noises. 5. By the internal move~ 
ments of the animals themselves, amongst 
which may be included the exercise of the ani- 
mal’s will. 
1. Temperature, §c—By far the greater 
number of luminous animals with which we 
are acquainted are riatives of warm climates ; 
but those inhabiting the ocean are seen in 
almost all latitudes, even in the coldest; al- 
though in these they are not so numerous, and 
give less light. No aérial insects give out 
light, in ordinary circumstances, excepting at a 
temperature of about 50° Fahr. and upwards ; 
and the higher the natural temperature, the 
brighter is the light emitted. 
In temperate climates the cmap ieee shine 
only in summer and autumn. L. noctiluca 
appears in this country between June and Sep- 
tember; L. splendidula, in Germany, is lumi- 
nous in May; and L. hemiptera so early as in 
the end of April. 
The light of pholas dactylus is strongest in 
summer; and that of marine animals in ge- 
neral is increased before storms. 
2. Solar light.—It is said that Scolopendra 
does not shine at night excepting it has been 
exposed during the day to solar light. A short 
time of exposure to the sun’s rays seems to be 
sufficient to refresh its luminous power, as (like 
all other light-giving animals) it secretes itself 
as much as possible during the day. It is 
stated by Burmeister,* with regard to the Lam- 
pyris Italica, that if it be kept some days in 
the dark it entirely loses its luminousness, but 
regains it on being again placed in the sunshine. 
8. Lunar light—Macartney remarked that 
luminous meduse generally retreat from the 
surface of the water at moon-rise. 
4. Abrupt collision with other bodies.— 
Marine luminous animals very readily emi 
their light on being struck by any moving body; 
so that one of the most commonly observed 
phenomena connected with this subject is the 
* Manual of Entomology, transl. by Shuckhard, 
p. 494, 
