This paper may be regarded as a continuation of the Cubomedusan studies pursued by Dr. F. S. Conant while in Jamaica, in 1896 and 1897, with the Johns Hopkins Marine Laboratory. His systematic and anatomical results have since been published as his Dissertation (“The CubomedusÆ”) by this University. Conant described this paper as Part I, hoping soon to add a second part on the physiology and the embryology, for which he had some notes and material at hand. Returning, however, to Jamaica with the laboratory, in 1897, he continued his physiological experiments, and preserved material for histological purposes. Upon the untimely death of Conant, his material and notes were placed in my hands by Professor Brooks, to whom I here take the opportunity of expressing my appreciation and sincere thanks for the honor thus conferred and for the many favors received.

In this paper I shall note at some length Conant’s physiological results and append his notes. I shall also add my results on the histology of the eyes and the sensory clubs in general, with some few facts on the histology of the tentacles. The embryology will be reserved for a future paper.

The forms used in the physiological experiments were Charybdea Xaymacana, one of the two species (see Literature V, a and b) first found and described by Conant; Aurelia aurita; Polyclonia and Cassiopoea. The greater number of Conant’s notes are on Charybdea, and were left by him just as taken at the time of experimenting. Many of these notes are highly interesting and in the main fit in well with Romanes’[I] and Eimer’s[IV] results.

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 Cassiopoea 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 Cassiopoea. 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 Cassiopoea. 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 Cassiopoea. 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:

The CubomedusÆ, as the name implies, approximate cubes, with their tentacles (four in Charybdea) arranged at the four corners of the lower face of the cube. These tentacles are said to lie in the interradii. Half way between any two points of attachment of the pedalia (the basal portions of the tentacles) and a little above the margin of the bell (cube), in a niche, hang the sensory clubs, one on each side, four in all. Each sensory club hangs in a niche of the exumbrella and is attached by a small peduncle whose axial canal is in connection with one of the four stomach-pockets and in the club proper forms an ampulla-like enlargement.

Each club is said to lie in a perradius, and, like the tentacles, belongs to the subumbrella. This is shown by the course of the vascular lamellÆ, bands of cells that, stretching through the jelly from the endoderm to the ectoderm all around the margin, form the line of division between sub- and exumbrella.

Each club has six eyes. Two of these on the middle line of the club facing inwards are called the proximal and distal complex eyes, to distinguish them from the four simple eyes that are disposed laterally, two on each side of the line of the two complex eyes. All of these eyes look inwards into the bell cavity through a thin transparent membrane of the subumbrella. Besides the eyes and the ampulla already mentioned, a concretion fills the lowermost part of the club, and a group of large cells, having a network-like structure and called network cells by Conant, fill the uppermost part of the club between the proximal complex eye and the attachment of the club to its peduncle (Plate II, Fig. 13). What is evidently nerve tissue, fibers and ganglion cells, fills the rest of the club, with two groups of large ganglion cells disposed laterally from the network cells. A sensory (flagellate) epithelium covers the club.

Most CubomedusÆ, among them Charybdea, have a velarium (comparable to the velum of the HydromedusÆ), a membrane of tissue that extends inwards at right angles all around the margin. This velarium, like a velum, has a central opening through which the water is expelled from the bell-cavity when the animal pulsates. In the perradii and in the angle between the velarium and the body wall, are the frenula, which give support to the velarium much like brackets support a shelf, except that here the brackets are above the shelf instead of below.

In the upper part of the bell is the stomach, with the phacelli in its interradii, and continued ventrally into the manubrium, or the proboscis. The cavity of the stomach is continued in the perradii through the four gastric ostia into the four stomach pockets, which occupy the sides of the bell and extend to the margin. Immediately below the gastric ostia, and in the bell cavity, are the suspensoria, one in each perradius. These support the floor of the stomach much as the frenula support the velarium, except that the suspensoria are placed under the shelf (to continue Conant’s figure) and not above it as are the frenula.

A nerve ring, underneath the epithelium of the subumbrella, passes from near the origin of each pedalium at the margin to the origin of the peduncles of the sensory clubs, a little above the margin, giving off a branch to each club. Eight ganglia are found in the course of this nerve. The four pedal ganglia lie near the bases of the pedalia, and are hence interradial; the four radial ganglia lie near the bases of the peduncles of the clubs, and are perradial. A small nerve, radial nerve, can be traced a short distance upwards from each radial ganglion. Underlying the epithelium of the frenula and the suspensoria are ganglion cells and nerve fibers in larger numbers than elsewhere (excepting the ganglia mentioned) in the subumbrella. Otherwise, ganglion cells and nerve fibers underlie the epithelium of the subumbrella, including the inner surface of the velarium, as also do muscle fibers, except in the perradii and in the region of the nerve, where the latter become interrupted.