Dr. Conant’s work on Charybdea, in 1897, was wholly done at Port Antonio, Jamaica. At first Conant had only varying success in obtaining Charybdea, scouring the harbor and neighboring water at all hours, only to obtain but few specimens. It was on the forenoon of August 7th, while we were dredging at the head of East Harbor with a steam launch, that many Charybdeæ were brought up in the dredge. This gave Conant a clue to their whereabouts and to the means of obtaining them, and from that time on he was able to obtain them in abundance. His first physiological experiments were begun on August 4th and continued thereafter at intervals of several days until his departure from Jamaica on September 6th. Dr. Conant usually performed his experiments during the second half of the forenoon, after the animals had stood for a few hours in the laboratory. The building that was rented at Port Antonio for a laboratory had, in the basement, a photographer’s dark-room, which was of great service to Conant in his experiments. The experiments on Aurelia, in 1897, were also performed at Port Antonio, between August 6th and 9th. The experiments on Cassiopœa were probably made at Port Antonio, where specimens were occasionally obtained. The notes on Aurelia and Polyclonia, in 1896, were taken at Port Henderson, between May 12th and June 27th. In his notes Conant speaks of Polyclonia and Cassiopœa. It is at present undetermined whether he really had both forms or whether he uses the two names for the same form. It seems likely that in 1896 he thought the form to be Polyclonia, while for some reason, in 1897, he supposed it to be Cassiopœa. I have examined several specimens of these medusæ brought from Port Antonio and find that they all have twelve marginal bodies and twenty-four radial canals, according to which (V, Haeckel’s System), they should be Polyclonia. Conant, however, speaks of removing sixteen marginal bodies, which seems to indicate that he had Cassiopœa. A careful classification of this form of medusæ found about Jamaica seems to be a desideratum. I suppose, however, that for our purpose in this paper it will make little difference which name is used, the two forms being so similar in form and structure. I have, therefore, decided to retain both the names used by Conant. For the complete anatomy of Charybdea the reader is referred to Dr. Conant’s dissertation, “The Cubomedusæ” (8b), or the _Johns Hopkins University Circulars_ (8a), both published by the Johns Hopkins Press. But, for the convenience of those who may be less familiar with Cubomedusan anatomy, the following brief summary of the anatomy of Charybdea is given: