1896.] BRITISH HTDEOIDS AND MBDTJS;!!. 46'/ 



AmpJiicodon ghbosus, Haeckel (1879). 



Amphicodon ampMpleurus, 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 Man, 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 me to identify the early stages as species already 

 described. 



The first stage has only one tentacle, to which belongs Steen- 

 strupia (Amphicodon) glohosa, Sars, but only those specimens 

 described with one tentacle. 



The second stage has a single group of two tentacles, to which 

 belongs Ooryne {Amphicodon) friiillaria, Steenstrup. 



The third stage (adult) has a single group of three tentacles, to 

 which belong certain specimens of Steenstrupia {Amphicodon) 

 glohosa with three tentacles and Amphicodon amphipleurus, Haeckel. 



The medusa first reproduces by means of numerous buds at the 

 base of the tentacles, and vrhen gemmation is about io cease ova 

 or spermatozoa appear upon the walls of the stomach. The sexes 

 are separate, and the ovum finally develops into a CorywiorpAn-like 

 hydi-oid. The development takes ])!ace inside the umbrella-cavity, 

 aud the hydra remains attached to the wall of the stomach until 

 two verticils of tentacles are formed. Steenstrup described the 

 medusoid Ooryne friiillaria from free-swimming specimens, and 

 also dredged a h3'droid 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 medusaa. He naturally considered this hydroid to 

 belong to the medusoid Goryne 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 may be difficult to recognize 

 the iiydroid form without its medusa-buds ; but with medusae, the 

 presence of tiie five longitudinal bands of nematocysts upon the 

 ex-umbrella of the medusa ought at onco to establish its identity 

 and to distinguish it from Corymorpha nutans. 



Valencia. — On the first day of tow-netting, April 5tli, 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 hydras either attached to the 

 stomach or free within the umbrella-cavity. 



30* 



