KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 5l. N:o ll. 37 
BROCH points out that the membranous development in the ÅA. digitalum var. nor- 
vegicum (= Erythropodium norvegicum) is also found in specimens of Alcyonium digi- 
tatum, and I have also found this in numerous specimens from Bohuslän, Sweden. In 
order to distinguish between ÅA. digitatum and the variety norvegicum, which he consider 
as species, BRocH very carefully examines the armature and finds considerable diver- 
gences. 
Before I ventilate the question of the difference in the shape of the spicules of the 
two forms, I will briefly refer to the different ideas held concerning the remarkable 
system of growth which is stated to be a characteristic of Hrythropodium norvegicum 
(sensu BRocH). 
As a result of v. Kocm's valuable investigations with regard to Sympodium coral- 
loides PALLAS, which he considers to be an Alcyomium that has adapted itself to its 
substratum, KUKENTHAL, in 1906, could greatly reduce the number of species of Sympo- 
dium, in as much as he considered a number of Sympodium-forms to be Alcyonium- 
species belonging to the sub-genus Erythropodium, which are distinguished by a low, 
membranous colony. He points out, at the same time, that the likeness between Sym- 
podium and Erythropodium should be considered as a phenomenon of convergence, due 
to singular conditions of life. He tentatively classifies Sympodium norvegicum KOR. 
and DAN., mostly on account of the appearance of the spicules, among Erythropodium. 
BrRocH confirms KUKENTHAL's opinion, but he has not yet explained the real differences 
between Sympodium and Erythropodium. 
As a result of my own investigations, I have come to a somewhat different concep- 
tion of these FErythropodium-species, in as much as, unlike KÖKENTHAL and BROocH, 
I do not admit that they belong to a constant sub-genus. (Compare p. 19.) I imagine 
that they are forms which have adapted themselves to the varying substrata, but which 
would otherwise be perfectly normal. TI obtain further support for this supposition of 
mine from the conditions existing in Alcyomium digitatum var. norvegicum. 
On tubes and shells of worms, mussel shells, coral trunks, etc., there are found the 
creeping colonies of Alcyonmium digitatum var. norvegicum, whose colonies often form 
membranes which completely enclose the substratum. "There are found in numerous 
cases, however, colonies of normal type, as regards their outward shape, with an armature 
which completely corresponds with that of A. digitatum var. norvegicum. I wish to point 
out that a great number of normal specimens, investigated by me, from the coast of Swe- 
den showed an armature corresponding with that of A. digitatum var. norvegicum. Con- 
sequently, as we find the spicules type of A. digitatum var. norvegicum in the normal 
colonies, the armature is not decisive of the question: Alcyonium digitatum or Erythro- 
podium norvegicum (sensu BRocH)? Nor is the mode of growth either, as we find the 
species now with membranous, now with normal colonies. 
BrRocH, however, has been able to distinguish two types of spicules, which are 
to be found in Alcyonium digitatum and A. digitatum var. norvegicum respectively. The 
transitional form between these types is not absent, and this holds good in particular 
in respect to the spicules from the bark of the colony. 
