KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 51. N:o |l. 61 
Forma typica: "The colony consists of an obvious trunk, with well-developed bran- 
eheswio (BIN Ijufigsr9v) 
Forma arctica: Trunk low, branches reduced. The anthocodiae generally situated 
directly on the trunk. (Pl. I, figs. 12 and 13.) 
Forma loricata: "Trunk almost totally reduced; anthocodiae placed close together 
on a short, wart-like trunk. "The basal part of the colony often membranous. (PI. IT, 
fig. 6.) 
Forma membranea: Trunk completely reduced. The colonies consist of membran- 
ous dises. The anthocodiae are scattered over the membrane. (Fig. 7.) 
To forma typica belong the great majority of the specimens of this species. Forma 
arctica contains, among others, Gersemia arclica (DAN.) and most of the specimens describ- 
ed as Gersemia abyssorum (DAN.). Forma loricata contains MARENZELLER'sS Gersemia 
loricata. Forma membranea contains the Clavularia frigida (DAN.) and Sympodium hya- 
linum GRIEG. 
It must, however, be observed that these forms can pass into each other, so that 
this classification cannot be considered as a fully satisfactory one, but it is given as 
evidence of the distinctions that exist between the numerous varieties. 
The canal system within the Gersemia fruticosa varies considerably, but it is found 
most regularly in forma typica. The connection between the coelenterons is partly in- 
direct, partly direct. The indirect connection, which is also fairly well developed, con- 
sists of short, endodermal, vertically lying strings in the walls between the coelenterons. 
They may at times have a very vigorous development and produce large cavities in the 
walls between the coelenterons. In the trunk and in the lower parts of the branches, 
where the coelenterons are few in number, the development of the indirect canals is 
more insignificant too, and the connection between the coelenterons unimportant. In 
the upper part of the branches, the indirect and direct connections change. The direct 
system consists of short, endodermal canals, which run horizontally and directly between 
the coelenterons. ”'The direct connection between the base of the younger coelenterons 
and the coelenterons of the surrounding, older polyps is particularly prominent. This 
is, of course, the result of the fact that the number of polyps decreases by the budding 
of a new polyp, and the cerowding among the coelenterons favours the production of direct 
connection. 'The budding of a new polyp does not occur on the direct canals, but from 
the indirect, which are numerous at the base of a new polyp, too. (Compare p. 14.) 
On account of the development of the branches and the more scattered situation 
of the polyps on the branches, the number of coelenterons in every branch is very insig- 
nificant. Solitary new polyps, or groups of them, occur here and there in the branches. 
In this case, the crowding among the coelenterons becomes great and changes occur 
in the relative position of the coelenterons. But gradually the coelenterons of the younger 
polyps disappear and the number of coelenterons is reduced. By means of this regula- 
tion of the space, excessive crowding is prevented, and the coenenchym between the coe- 
lenterons nearly always retain a constant thickness. When new polyps occur and the 
erowding becomes great, the direct connection predominates, but, by degrees, it is replaced 
by the indirect, when the space between the coelenterons once more grows larger. This 
