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Show 1896.1 • BRITISH HYDROIDS AND MEDUSAE. 467 Amphicodon globosus, Haeckel (1879). Amphicodon amphipleurus, Haeckel (1879) ; Garstang (1894); Allen (1895). The different stages in development of this medusa having been taken in localities far apart, and the wrong hydroid form assigned to one of them, has led to six distinct species being recorded. Haeckel retains four of these and places two amongst the synonyms. I have recently given an account of this interesting medusa in the Eeport on the Medusae of the Isle of M a n , and here only give a summary with some additional notes on the occurrence of the medusa at Plymouth and Valencia Island. The great abundance of this medusa at Port Erin during 1893 and 1894 enabled m e to identify the early stages as species already described. The first stage has only one tentacle, to which belongs Steenstrupia (Amphicodon) globosa, Sars, but only those specimens described with one tentacle. The second stage bas a single group of two tentacles, to which belongs Coryne (Amphicodon) fritillaria, Steenstrup. The third stage (adult) has a single group of three tentacles, to which belong certain specimens of Steenstrupia (Amphicodon) globosa with three tentacles and Amphicodon amphipleurus, Haeckel. The medusa first reproduces by means of numerous buds at the base of the tentacles, and when gemmation is about to cease ova or spermatozoa appear upon the walls of the stomach. The sexes are separate, and the ovum finally develops into a Corymorpha-like hydroid. The development takes place inside the umbrella-cavity, and the hydra remains attached to the waU of the stomach until two verticils of tentacles are formed. Steenstrup described the medusoid Coryne fritillaria from free-swimming specimens, and also dredged a hydroid having a single verticil of tentacles, and medusae attached to it, without tentacles, but with an oblique margin to the umbrella-one of the characteristic features of the free-swimming medusae. H e naturally considered this hydroid to belong to the medusoid Coryne fritillaria. It is clear, however, from the development of the hydroid within the umbrella-cavity, that the hydroid must have two verticils of tentacles. The hydroid has not yet been taken in the British area, but it is evident from the distribution of the medusoid form that it must exist in more than one locality. It m a y be difficult to recognize the hydroid form without its medusa-buds ; but with medusae, the presence of the five longitudinal bands of nematocysts upon the ex-umbrella of the medusa ought at once to establish its identity and to distinguish it from Corymorpha nutans. Valencia.-On the first day of tow-netting, April 5th, a single specimen was taken, and about two dozen more during the next few days, but not one was seen after April 16th. The specimens were similar to those taken at Port Erin. Some had ova upon the wall of the stomach; others had young hydrae either attached to the stomach or free within the umbrella-cavity. |
