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Show 462 MR. E. T. BROWNE ON [Mar. 17, Fam. BouGAiNviLLiD.as. PERIGONIMUS REPENS (Wright). Hydroid Form. Atractylis repens, Wright* (1858) ; Alder* (1862). Perigonimus repens, Hincks* (1868) ; Allman* (1872) ; Winther (1880); Duerdin(1893); Garstang* (1894). Perigonimus minutus, Allman* (1863); Hincks* (1868); Allman* (1872). Medusoid Form. Perigonimus repens, Crawford (1895). At Plymouth, on September 2nd, 1893, I placed a colony of Perigonimus repens in a jar of sea-water. On the following day about a dozen medusae were budded off. On the 13th another two dozen were swimming in the jar from the same colony. None of the medusae showed any signs of further development after their liberation from the hydroid colony. The umbrella of the medusa is about f mm. in length and width. There are two opposite perradial tentacles and two opposite per-radial bulbs, without tentacles. Some of the specimens have a knob at the aboral end of the umbrella. The knob varies in size and shape in different individuals, in a few it is absent. Mr. W . Garstang sent me a colony from Plymouth, on March 17th, 1894. On the 19th two medusae were budded off, one with a short knob at the aboral end of the umbrella, the other without a knob. Unfortunately I was not able to keep these medusae alive long enough to observe any further changes. Wright (1861) states that he has kept the medusa until it had four perradial tentacles and four interradial bulbs. Allman (1863) described another hydroid, Perigonimus minutus, which, he states, is very much like Perigonimus repens. The chief difference is in the shape of the medusoid, which has a constriction across the aboral end of the umbrella. The figure given by Allman of this medusa agrees with the specimens with a conical knob, bred in my jars. Hincks (1868) has placed Perigonimus minutus as a synonym of Perigonimus repens; but Allman (1872) has again separated them iuto two distinct species. As I have obtained from the same colony medusae similar to Wright's figures of Perigonimus repens and to Allman's figures of Perigonimus minutus, I do not now see any reason for their separation into two distinct species. DISTRIBUTION. Denmark, Baltic Sea, Winther (H). Heligoland, Hartlaub (H). Scotland-Shetland Islands, Allman (H). St. Andrews, Crawford (M). Firth of Forth, Wright (H). England-Cullercoats (Northumberland), Alder (H). Plymouth, Garstang and E. T. B. (H). Ilfracombe, Hincks (H). Ireland-S.W. Coast, Buerdin (H). |
