850 
“nite spots. The utility in this case is not 
certainly known, but two suggestions may 
be made, one to the effect that the light at- 
tracts the mate and thus serves the purpose 
of attractive coloration ; the other that it 
attracts the prey and serves the purpose of 
alluring coloration. 
A very large number of crustaceans are 
highly phosphorescent. Many of these have 
large eyes and are particularly active in 
movement and voracious in appetite. They 
feed on minute organisms for the most part, 
and it can hardly be doubted that they 
often use their phosphorescent powers for 
the purpose of illuminating their surround- 
ings and revealing their prey. Here again 
it is probable that the strangely attractive 
power of light serves a definite purpose in 
the life economy of the animal. 
Among the mollusca we have few in- 
stances, so far as I know, of phosphorescent 
organs. At the Detroit meeting of the 
American Association for the Advancement 
of Science, Professor William EH. Hoyle, of 
England, read an exceedingly interesting 
paper on certain organs possessed by ce- 
phalopods secured by the Challenger. These 
organs were regarded as phosphorescent by 
Professor Hoyle, who described a highly 
specialized apparatus designed to reflect 
light from the phosphorescent bodies down- 
ward to the bottom over which the animal 
passed. In this case it appears that there 
is not only a light, but also a reflector, an 
efficient bull’s-eye lantern for use in hunting 
through the abyssal darkness. Among the 
worms are many forms possessing a high 
degree of light-emitting power, which may 
be either attractive, alluring or directive in 
function, and thus of direct advantage to 
its possessors. 
Most of the echinoderms, although not 
truly fixed, are not capable of rapid loco- 
motion, and we are, therefore, not surprised 
to find few references to phosphorescence 
in connection with theme Perhaps the 
SCIENCE. 
[N.S. Vou. XIII. No. 335. 
most active of this group are the serpent 
stars, and it is interesting that the only 
account that I find of phosphorescence in 
the echinoderms is Agassiz’s description of 
a serpent star, which he says ‘is exceed- 
ingly phosphorescent, emitting at the joints 
along the whole length of its arm a bright 
bluish-green light.’ 
Coming to the ccelenterates, we find many 
notable phosphorescent organisms. The 
ctenophores and medusze comprise the 
greater part of the free swimming members 
of this subkingdom, and it is among these 
that we encounter amazing displays of the 
living light. The most brilliant exhibition 
of phosphorescence that I have seen was 
caused by immense numbers of ctenophores 
in Bahia Honda, Cuba. The animals kept 
in a compact body, producing a maze of 
intertwining circles of vivid light. The 
phosphorescence may help to keep them 
together, and thus serve the purpose of 
directive coloration among vertebrates and 
insects. This same explanation may apply 
to many of the phosphorescent medusze. 
In the subtropical Atlantic hundreds of 
square miles of the surface are thickly 
strewn with a medusa, Linerges mereurius, 
which glows like a living coal at night. 
In general, it may be said that phospho- 
rescence is found abundantly in free swim- 
ming marine animals, and serves the same 
purpose as protective, aggressive and allur- 
ing coloration, and at the same time, in 
many cases, aids in securing prey by illu- 
minating its retreat. 
We come, now, to a consideration of the 
phosphorescence of the fixed animals of the 
deep sea and its uses. Most of the light- 
emitting organisms of this group belong to 
the subkingdom celenterata. The sea- 
pens are mentioned by several writers as 
being especially brilliant in their flashes of 
light. The gorgonians, or flexible corals, 
are often phosphorescent, and Agassiz says: 
‘Species living beyond 100 fathoms may 
