As we have seen, the light emitted by animals, plants, and minerals, of whatever cause, presents much that is mysterious; and the problem of animal phosphorescence would seem no nearer being solved to-day than it was fifty years ago. This is perhaps due to a lack of study and investigation. A glance at the appended bibliography shows that much has been written upon the subject; but it is only within the last decade that serious work in this direction has been done, typified in the superb work of Dubois, and the papers and monographs of the other scientists mentioned. The naturalists of the “Albatross,” the government exploring steamer, are to make investigations regarding the luminosity of the Pacific, during the forthcoming tour on the western coast. The French Academy of Sciences offers this year a prize of three thousand francs for the best paper upon animal phosphorescence. From this it would appear evident that the phenomenon is creating renewed or increasing interest, and in the following years will be the subject of much study and investigation; and we may expect in the near future to have not only its cause explained, but possibly to see a practical application of its possibilities to the wants of mankind. APPENDIX. [1] PAGE 5.--_Noctiluca._ This interesting little creature belongs, in the natural arrangement as now recognized by science, to the first grand division of the animal kingdom. Simple as it is, it is not so completely without organs as some which form the first groups of this first division, as it has a whip-like organ, which gives name to its group, the _Flagellata_, or flagellate infusorians. These monads, as they are also called, are represented by a species of _Noctiluca_ in our North-American waters off the coast of Maine. Huxley regards its luminous property as given out by the peripheral layer of protoplasm which lines the cuticle. M. Giglioli of Bologna, Italy, in a letter to the author, says, “I have distinguished three modes of marine phosphorescence, very distinct, which present a great number of varieties. These are,-- “(_a_) Diffused homogeneous milky light. “(_b_) Luminous points, sparkling and inconstant. “(_c_) Luminous disks, with light generally fixed, and not sparkling. “In one case the sea seemed on fire, and dolphins seemed to be fire. “Again, the sea seemed to acquire an oily consistence, giving out soft homogeneous light, of a milky color, tinted with green or bluish. It is perhaps the least frequent, but most striking. It is due to the presence of noctiluca. It often resembled incandescent rain falling from the paddle-wheels of steamers.”