these specimens, the free filaments emerging singly, not in bunches, the cells of 
these filaments being longer, the chromatophores of the long cells being sometimes: 
partly spiral, the sporangia never being terminal on the principal filaments, give 
these specimens an appearance so different from those growing in Sertularia pumila 
that one is tempted to regard them as a distinct form. On the other hand, it must 
be admitted that the said Abietaria abietina covered with numerous free filaments 
of the described appearance bore also shorter and very short filaments with terminal 
sporangia, agreeing perfectly with those typical of the species. It must therefore be 
assumed that the species under particularly favourable conditions, which are some- 
times realised when it is growing in Abietaria abietina, produces longer fertile fil- 
aments with longer cells and without terminal sporangia. These filaments remind 
one rather of Rhodochorton chantransioides Rke. which, as shown by Kyrın (Z. 
Kenntnis ein. schwed. Chantransia-Arten, Botan. Stud. tilägn. Kjellman, Upsala 1906, 
p. 118) must be regarded as the asexual form of Chantransia efflorescens, an opinion 
which I have supported in 1909 (Mar. Alg. D. I, p. 137). Monosporangia were, how- 
ever, not found in the form growing in Abietaria abietina, and the free filaments of 
this plant differed otherwise by greater thickness (6,5—8 u), by the shape of the 
chromatophores being only exceptionally and partly spiral and by the tetrasporangia 
being larger, 25—30 w long, 12—17 w broad. 
The sporangia in the specimens growing in Sertularia pumila were 17—-21 (25) u 
long, (11) 13—15,5 w broad; in those growing in Sertularia pumila and Tubularia 
they were 17—30 (31) w long, 12—19 (20) u broad. The fact that the size of the 
sporangia is rather variable in the same specimen suggests that the sporangia in- 
crease in size after division. 
Kuckuck found as a rare case a hyaline hair, like those common in Acroche- 
lium (l. c. p. 17, fig. 2E). I never observed these organs. 
The great resemblance with Acrochetium efflorescens suggests that the species 
might perhaps be referred to the genus Acrochætium. 
A sponge dredged in Skagerak off Hirshals (possibly Chalina oculata) showed 
some purple spots, the largest abt. 11/2 cm long. These spots are due to an alga 
growing in the chitinous skeleton in a similar manner to Rhodochorton in the hy- 
droids, and probably identical with this species. They consist of branched filaments, 
mostly running immediately under the surface, but also deeper, partly distinct, partly 
fusing together in parenchymatous plates. Some cells showed foldings of the walls. 
Free filaments were not found, only numerous short round protuberances, prob- 
ably checked rudiments of free filaments. For want of fructification a conclusive 
determination is not possible. 
The species has been found in all the Danish waters with the exception of the 
inner parts of the Baltic, from low-water mark to 38 meters’ depth. It has been found 
with sporangia in all depths and in all seasons: in the specimens growing in Abie- 
taria collected in September and October in the North Sea and Skagerak, the spor- 
