No. 394.] ZHE UTILITY OF PHOSPHORESCENCE. 795 
strangely attractive power of light serves a definite purpose 
in the life economy of the animal. 
Among the Mollusca we have few instances, so far as I know, 
of phosphorescent organs. Lamellibranchs, however, are largely 
vegetative, impassive animals. The Gastropoda are more active, 
but still slow in movement compared with most animals. 
Among the Cephalopoda are a number of highly specialized 
and swift-moving forms, and here, if anywhere among mollusks, 
we should expect to find phosphorescent organs. At the Detroit 
meeting of the American Association, Professor William E. 
Hoyle, of England, read an exceedingly interesting paper on 
certain organs possessed by Cephalopoda secured by the Cha/- 
lenger. 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 Vermes 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 locomotion. Perhaps the most active animals 
of this group are the serpent stars, some of which are able not 
only to crawl rapidly, but actually to swim with considerable 
facility. It is therefore interesting to note that the only phos- 
phorescent echinoderm that I can find any account of belongs 
to the Ophiuridz, and is described by Agassiz as “exceedingly 
phosphorescent, emitting at the joints along the whole length 
of its arms a bright, bluish-green light.” Its utility can only be 
conjectured. If, as in the case with many of its allies, its 
life is spent crawling among the branches of phosphorescent 
gorgonians, the protection thus secured would certainly be 
advantageous. 
Coming now to the Ccelenterata, we find many notably phos- 
phorescent organisms. The ctenophores and medusæ com- 
prise the greater part of the free-swimming members of this 
