1896. ] BRITISH HYDROIDS AND MEDUS2. 477 
Claparéde discovered it off Arran Island, in the Firth of Clyde, 
during September 1859. 
I do not think that Claparéde’s medusa is a distinct species, but 
a stage in the development of Lizzia blondina. 
Distrisution. Heligoland, Haeckel. 
Scotland—Shetland Islands, Forbes. Bell Rock (East coast), 
M*Intosh, Arran Island, Claparede. 
England—Plymouth, #. 7. B. Fowey, Peach. Falmouth, Val- 
lentin. Isle of Man, Browne. 
Ireland—Valencia Island, Z. 7. B. 
MARGELLIUM OCTOPUNCTATUM (Sars). 
Cyteis octopunctata, Sars (1836) (1846). 
Inzzia octopunctata, Forbes (1848); Peach (1849); Agassiz 
(1862); Béhm(1878); Clubb (1886); M‘Intosh (1890) ; Vallentin 
(1893). 
Inzzia grata, Agassiz (1865). 
Rathkea octopunctata, 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 the ova after leaving the medusa is 
at present unknown. The ovum may give rise to a hydroid form 
or develop directly into a medusa. The young medusz on leaving 
their parent have not always the same number of tentacles. 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 
(Cytwis octopunctata) from specimens with three tentacles in all 
the groups (= athkea 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 Rathkea. 
I have already shown, in the Report on the Medusz of the Isle 
of Man, that Forbes was right in regarding his specimens as 
identical with the meduse described by Sars as Cyt@is octopunctata. 
Garstang has also shown that Haeckel was wrong in separating 
these medusz into two distinct genera, 
