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Show 826 MR. E. T. BROWNE ON BRITISH MEDUSA. [Nov. 16, filiform cirrus was situated on the outer side of a tentacle-bulb, or upon the " spur." The cause of this abnormal position I was able to trace from the early stages. The tentacles do not all occupy exactly the same position on the margin ; some develop very close to the inner side of the margin. The filiform cirri are close to the outer side of the margin, and, consequently, when a tentacle-bulb makes its appearance close to the inner margin and opposite a cirrus, in its subsequent growth it carries the cirrus in an outward direction. All the Valencia specimens were quite colourless to the naked eye, but under the microscope a narrow band of a yellowish-brown colour is seen at the base of the ring-canal, and a narrow streak of the same colour is also visible in the basal bulbs of the tentacles. DIPLEUROSOMA HEMISPHCERICUM (Allman). (Plate XLVIII. figs. 3, 3 a.) Ametrangla hemisphcerica, Allman (1873). Dipleurosoma Irregulare, Haeckel (1879); Haddon (1885). During m y visits to Valencia in 1895 and 1896 I found a few specimens of this species. Allman, in the description of the species, states that there are three main radial canals with branches ; some of the branches enter the ring-canal and others terminate blindly. Haeckel found some specimens at Brighton, one of which agreed with Allman's description, and the others showed considerable variation in the arrangement of the canal-system. The Valencia specimens also show that the canal-system, which I now only intend to describe, is very variable. The specimen which approaches nearest to Allman's description has three large radial canals, with lateral branches, and also two smaller canals leading from the stomach to the ring-canal (fig. 10, p. 827). The umbrella of this specimen measures 8 m m . in diameter, and the ova are just visible upon four of the canals. Another specimen, of which I have given a figure (Plate XLVIII. figs.3,3«) shows another type of canal-system. There are four large canals, which divide the umbrella into four equal parts, and four smaller canals, interradially situated, one of which has reached the ring-canal and the other three terminate not far off. The gonads have not yet commenced to develop. The umbrella is about 8 m m . in width and 4 m m . in length. Avery irregular system of canals is shown in another specimen (fig. 11, p. 827). This has eight radial canals leaving the stomach and joining the ring-canal, and some of these canals have short lateral branches, which probably by further growth finally reach the ring-canal. In a damaged specimen I have counted as many as eleven canals entering the ring-canal. A slightly damaged specimen of a male shows that the generative cells form a large oval mass, on, at least, five of the radial canals, and that the |