MARINE ZOOLOGY 2. MEDUSit Gelatinous, bell or disc-shaped, transparent, often with radiating or marginal streaks of brilliant colours ; not colonial ; free-swim- ming, often in large shoals. The smaller medusae are produced by lateral budding from various Hydroid stocks, es- pecially such forms as Podocoryne, Syncoryne, Perigonimus, Bougainvillea, Corymorpha, Clytia, Obelia, and Campanularia. Wher- ever these Hydroids occur their medusae may be obtained either from the Hydroids them- selves at the proper season, or with a muslin net at the surface of the sea. Other meduss may also be found whose larval or Hydroid phases are not yet determined. The larger medusae, which are so frequently cast ashore after strong sea-breezes in the summer months, do not always exhibit a similar alternation of stages in their life-history ; but Aurel'ia and Chrysaora are known to be produced by a remarkable process of succes- sive fission from minute hydra-like polyps which form extensive colonies on old oyster- shells and similar objects. My present list of local medusae is very brief from the scantiness of existing records. A. Hydromedusis I. Obelia, sp. The medusa of Obelia is readily recognized by its perfectly flat and disc-shaped umbrella, its short quadrate manubrium, its numerous short marginal tentacles (24 to 1 14, according to age), and its eight marginal otocysts, as well as by its brilliant phosphorescence. It varies in diameter from i to 6 mm. according to age. Under the name Eucope lucifera, Schultze records a number of small medusae derived from Obelia colonies which were taken in a surface net off Cromer during the Pommerania cruise. Haeckel has attempted to refer the various described types of Obelia medusae to their respective Hydroid stocks, basing his distinctions on the length of the tentacles and manubrium relatively to the umbrella radius, and on the position of the ovaries on the radial canals, i.e. whether in the proximal, middle or distal thirds of the course of the canals. As some of these differences are known to be due to growth-changes, it is doubtful how far they can be relied upon as specific characters. The only safe plan of identification will be to rear the medusas of various Obelia colonies to maturity in aquaria, until the characters of several species are known at successive ages. B. Discomedusa 2. Aurelia aurita (Linn.). Umbrella very slightly arched ; margin beset with numerous very short tentacles and notched at eight equidistant points ; transparent, the ovariesshowing through as four horse-shaped masses of a violet or purplish colour. Com- mon close around our coasts. The Pom- merania met with this and the next species in all parts of the North Sea, but the individuals found far from shore were scattered and of small size. 3. Cyanea capillata (Linn.). Umbrella slightly arched, disc-shaped ; margin divided as in Aurelia, but beset with long slender tentacles. Colour usually yellowish brown or reddish yellow. Common all round the North Sea. The beautiful blue Cyanea Lamarckii is far rarer than the preced- ing species, and has not yet been recorded for Norfolk. C. Lucernarians Sheringham has been reported as a good locality for Lucernarians, but I have no record of the species found there. A minute long- stalked Lucernarian obtained on the Norfolk coast by Mr. Geldart appears to be a young specimen of Depastrum cyathiforme, but the record needs confirmation. n. CTENOPHORA Jellyfishes devoid of a muscular umbrella and provided with eight vertical (meridional) rows of iridescent paddles. 1 . Pleurobrachia pileus, Modeer. Shape ovoid ; size usually ^ to | inch. Provided with a pair of flexible fringed retrac- tile tentacles. Off Cromer and in Yarmouth harbour, common (P.). 2. Bero^, probably ovata, Eschscholtz. Shape cylindrical ; size usually from i to 3 inches. No tentacles. Off Cromer, rare (P.). m. ANTHOZOA Sea Anemones and Corals Nomenclature : Gosse, British Sea Anemones and Corals, i860 I. Alcyonium digitatum. Commonly known as * dead men's fingers,' 'cow's pap,' etc. Abundant in the deeper waters, but not recorded nearer than twenty miles north-west of Cromer (P.), though doubt- less often cast ashore. 81
