1896.] BRITISH HYDE0IJD8 AND ItBDUSiE. 477 



Claparede discovered it off Arran Island, in the Firth of Clyde, 

 during September 1859. 



I do not think that Claparede's medusa is a distinct species, but 

 a stage in the development of Lizzia blondina. 



Distribution. Heligoland, Haeckel. 



Scotland — Shetland Islands, Forbes. Bell Eock (Bast coast), 

 M'Intosh. Arran Island, Claparkle. 



England— Plymouth, E. T. B. Fowey, Peach. Falmouth, Val- 

 lentin. Isle of Man, Browne. 



Ireland — Valencia Island, E. T. B. 



Mabgelliuji OCTOPUNOTAT0M (Sars). 



Gytceis octopunctafa, Sars (1836) (1846). 



Lizzia octopimctata, Forbes (1848); Peach (1849); Agassiz 

 (1862) ; Bbhm (1878) ; Clubb (1886) ; M'Intosh (1890) ; Vallentin 

 (1893). 



Lizzia grata, Agassiz (1865). 



Rathkea ootopimctata, Haeckel (1879) ; Giard (1888) ; Garstang 

 (1894): Allen (1895;. 



Margellium octopunctatum, Haeckel (1879) ; Browne (1895). 



Margellium gratum, Haeckel (1879). 



The medusa first reproduces itself by means of buds upon the 

 stomach, and when it reaches the adult condition either ova or 

 spermatozoa appear upon the wall of the stomach ; the sexes being 

 separate. What becomes of tlie ova after leaving the medusa is 

 at present utiknown. The ovum may give rise to a hydroid form 

 or develop directly into a medusa. The young medusae on leaving 

 tlieir parent have not always the same number of tontacles. There 

 are usually three tentacles in each of the four perradial groups, but 

 occasionally only two ; the interradial groups may have either two 

 or three tentacles, rarely only one. As the medusa grows the 

 perradial tentacles increase to five in each group, and the inter- 

 radial tentacles to three in each group. The change in the 

 number of tentacles has led to some of the early stages being 

 described as distinct species. Sars first described the medusa 

 (Oy talis octopunctata) from specimens with three tentacles in all 

 the groups {^=liathjcea of Haeckel). Forbes described specimens 

 (Lizzia octopunctata) having either two or three tentacles in the 

 perradial groups, and three tentacles in the interradial groups. 

 Forbes regarded these specimens as belonging to the same species 

 as those described by Sars. Haeckel, however, has separated these 

 specimens into two genera : those with two tentacles in the perradial 

 groups are placed in the genus Margellium ; the others in the 

 genus IlathJcea. 



I have already shown, in the Eeport on the Medusae of the Isle 

 of Man, that Forbes was right in regarding his specimens as 

 identical with the medusse described by Sars as Gytceis octopwictata. 

 Garstang has also shown that Haeckel was wrong in separating 

 these medusse into two distinct genera. 



