SAS 
Hildenbrandia prototypus. Here it forms velvety patches of the usual aspect, but the 
erect filaments are short, about 1 mm, simple or little branched, thin, usually 7—10 u 
broad, the cells being about twice as long as broad (fig. 328). The lower part of 
the filaments are sometimes moniliform, consisting of short inflated cells scarcely 
longer than broad. These supralittoral specimens thus show no resemblance to 
Rhodochorton islandicum. — The species is usually found growing on rocks and 
stones, further on wood (in harbours), more rarely on Mytilus and the hapters and 
stipe of Laminaria hyperborea and L. digitata, further on Phyllophora Brodiwi, partly 
on a Bryozoan on this. — In three localities in the North Sea, W. of the Limfjord, 
very small specimens of a Rhodochorton were found growing on Flustra foliacea, 
forming small tufts reaching only a height of 180 «. They were supposed to be 
much reduced specimens of Rh. Rothü. The creeping filaments were often more or 
less densely united into a pseudoparenchymatic layer reminding one somewhat of 
that in Rh. membranaceum, but they were creeping on the surface of the skeleton 
of the Bryozoan, not penetrating it as in the last-named species, and the free, 
erect filaments were thicker (6—9 «, most frequently 7—8 w). Sporangia were not 
present, only stipes of shed scattered sporangia (Sept.—Oct.). — The species has been 
met with in almost all the Danish waters and is probably widely spread except in 
the Limfjord (and other fjords). 
Localities. Ns: eE, 12 miles N.W. by N. of Bovbjerg light-house, 16 m; dZ, 17 miles W. °/s N. 
of Lodbjerg light-house, 36 m; eQ, 8 miles NW. by W. ‘/2 W. of Lodbjerg light-house, 27 m, in all lo- 
calities on Flustra foliacea. — Sk: Hirshals, reef, under Fucus. — Kn: Tyskerens reef and N.E. reef 
by Hirsholm, Frederikshavn, moles; Busserev; off Laurs Rev, c. 10 m, on Laminaria digitata; Osterby 
harbour, Læso; fG, Tonneberg Banke, 15 m. — Ks: Grenaa, harbour; Nordvest-Renden by Hesselo, on 
Phylloph. Brodiæi (Lyngbye). — Sa: PG, west of Hatterrev, c. 8m; north side of Refsnæs, 19 m, on 
Mytilus (C. H. Ostenfeld). — Lb: Baaring, harbour; Bogense, harbour; Fredericia (Hofm. Bang); Middel- 
fart, harbour; Kongebro; Snoghøj, harbour; dH’, east of Hesteskoen, 18—19 m, on Phyllophora. — Sb: 
Kjerteminde, harbour; near Sprogø, 10—28 m (C. H. Ostenfeld); near Vresen, on Mytilus, 8—9 m (C. 
H. Ostenfeld); US’, Langelandsbelt, 20 m. — Su: København, Frederiksholms Kanal. — Bm: Køge, 
harbour. — Bb: Davids Banke, 29 m; near Hammershus, up to 2m above the sea level; Ro, “den 
vaade Ovn”, at the entrance to “den sorte Gryde” up to 3 m, Helligdomsklipperne (Liebman, J. Hartz, !); 
Græsholm at Christiansø, up to 2 m above sea level. 
3. Khodochorton membranaceum Magnus. 
Callithamnion (Rhodochorton) membranaceum Magnus, Die botan. Ergebnisse der Nordseefahrt 1872. 
II. Jahresber. d. Komm. z. Unters. d. deutsch. Meere in Kiel. Berlin 1874, p. 67, Taf. II figs. 7—15; 
Collins, Notes on New England Marine Algæ II, 1883, p. 56 (Bull. Torr. Bot. Club, Vol. X); Ström- 
felt, Botaniska Notiser 1887, p. 109; Kolderup Rosenvinge, Gronlands Havalger 1893. Meddel. om 
Gronland III. 3, p. 794; Kuckuck, Beitr. 1897, p. 13. 
As shown by CoLLıns, STRÖMFELT and Kuckuck (ll. cc.), the vegetative fila- 
ments live in the chitinous walls of various Hydroids. In the Danish waters the 
species is most frequently found in Sertularia pumila, further in Abietaria abielina 
(North Sea, Skagerak and Kattegat), Tubularia, Hydrallmania falcata (North Sea), 
