Just above the smaller eye there lies a mass of cells of peculiar structure (Fig. 69, _nc_). They are of a rounded polygonal contour, with a comparatively small circular nucleus in the centre, and are found in this region only. In and amongst them bundles of fibrous tissue are found in the sections, which pass from the surface cells to the supporting lamella. Claus describes the contents of these cells as coarsely granular protoplasm and says they cannot be taken for ganglion cells. He is inclined to believe that they play the part of a special supporting tissue. Schewiakoff, on the other hand, is convinced that they are ganglion cells, and finds processes passing out from them (’89, Taf. II, Fig. 22). I find, however, that the cell contours are perfectly regular and clearly without processes, and it is incomprehensible to me how, if his material was at all well preserved, he could for a moment have taken them for the same thing as the big multipolar ganglion cells with large nucleus and nucleolus which lie in about the same region and were correctly described and figured by Claus but are not specially mentioned by Schewiakoff. I cannot agree with Claus, however, that their contents are composed of coarsely granular protoplasm. That which appears such by low magnification shows itself under high powers to be a beautiful network with thickenings at the nodes of the meshes, which is brought out very plainly by a cytoplasmic stain such as Lyons blue. Around the nucleus is seen a more or less well-defined clear zone. What the function of the cell is remains as unknown to me as to Claus and Schewiakoff. There is left one more point in reference to the nervous system upon which I wish to say a word. Claus and Schewiakoff both describe the wall of the crystalline sac as structureless, formed by the bare supporting lamella. The credit is due to H. V. Wilson of finding in Chiropsalmus that it has a special lining of epithelial cells, which he figures as a continuous, flattened layer. In both Charybdea and Tripedalia I find traces of the same in nuclei here and there, but whether they are the remains of a once continuous layer or not the sections do not show satisfactorily. This ends the account of what it seemed worth while to say at present upon the nervous system. In concluding, the writer wishes to express his thanks for the help afforded by Dr. Wilson’s notes, in particular on the subject of the vascular lamellæ, and desires to make especial acknowledgment of his indebtedness to Professor Brooks, whose suggestions, based upon many years of experience with the Medusæ, have been most welcome and helpful, and whose evidences of unfailing kindliness, both in Jamaica at the time the material was obtained and in Baltimore when it was being studied in the laboratory, take a most honored part in the pleasant memories associated with the work. LITERATURE REFERRED TO.