WEBER-VAN BOSSE—MARINE ALG A 293 
monosiphonio brevi tantummodo restante. hallo sympodiali, radiato; ramis 
cum divergentia {. Primo segmento libero ramorum ad basim satis magnam 
cellulam incremento basipetal disjungente. Cellulis centralibus magnis, hyphis 
numerosis angustis cinctis. Stichidiis ramulis penicillorum sessilibus; 8-10 sporas 
im unoquoque segmento ferentibus. Cystocarpiis et antheridiis ignotis. 
Coetivy, reef ; in alcohol. 
Cargados Carajos, 47 fms.; dry specimen. 
This new Dasyopsis attains a height of 2°5 cm., and consists of a small tuft of primary 
ascending cylindrical axes or stems, that finally become horizontal and give rise to new 
ascending ones. The tufts, on growing older, become more or less intricate, but I 
never saw the fronds anastomose. Dasyopsis aperta is a good species for the study of 
the peculiar Dasyopsis structure, because the cells are large, even at the apex of the 
shoot. It is sufficient to spread the alga on the slide and to tear off carefully with 
a needle the surrounding penicilli to see plainly the row of central cells, each carrying 
a pushed aside apex and its first branch whose lowest cell builds up the sympodium. 
These branches stand spirally around the main axis, so far as I could ascertain, with 
a divergence of 4, and carry long, incurved filaments at their top, which form together 
the peuicillus. The first cell, after the branch has been pushed aside, cuts off a cell at 
its base (Pl. 18. fig. 32, m); this is the mother-cell of the downward-growing hyphex, 
which are at first almost as large as the cells of the central axis or tube. At the top ofa 
stem or axis, where the mutual position of the different cells is still unaltered, the central 
tube appears to consist of a central and four pericentral cells, but on following the 
pseudo-pericentral cells to their origin, it will be clearly seen that they are downward- 
growing hyphe, arising from the first free cell of the pushed aside branch. The sym- 
podial axis is afterwards covered by a thick layer of smaller hyphz, which by growing 
between them alter the original position of the cells. 
The stem or main axis is cylindrical, though tapering towards its apex, which is 
densely covered with penicilli; these, however, soon fall off, and the base of older stems 
is almost denuded, though not entirely, for remnants of the basal portion of the penicilli 
often remain. 
The sessile stichidia are borne on the side-branches of the penicilli; they are 
cylindrical and, when the tetrasporangia have acquired their full size, a little torulose. 
I counted from 6-8 sporangia in different segments; and the whole is crowned by one 
or two barren cells. Neither cystocarps nor antheridia were seen. 
There are, according to Falkenberg*, two other species of Dasyopsis, which, like 
D. Stanleyi and D. aperta, have penicilli facing every way, namely Dasyopsis spinella 
and D. cervicornis. From the first both D. Stanleyi and D. aperta differ in the absence 
of the little spines that have given D. spinella its specific name, and from D. cervicornis 
in the shape of their stem, cylindrical throughout, not angular at the insertion-point 
of the penicilli. 
* Falkenberg, “ Die Rhodomelaceen des Golfes yon Neapel,” 1901, p. 667. 
SECOND SERIES—ZOOLOGY, VOL. XVI. 38 
