. The Danish Ingolf-Expedition. Scientific expeditions; Arctic Ocean. PORIFERA. II. 145 preserved to any greater extent, circular openings of a diameter of about o-5mm are found in it, also a few smaller ones, and these openings must be regarded as oscula. In the thicker, irregularly leaf- shaped specimens a few wide perpendicular canals are also often found, opening in the edge; but I am not quite sure, whether the question is here of real oscular canals, or they are secondary canals arisen by coalescing. In the membrane coating these canals, dermal spicules are found and also pore- shaped op
. The Danish Ingolf-Expedition. Scientific expeditions; Arctic Ocean. PORIFERA. II. 145 preserved to any greater extent, circular openings of a diameter of about o-5mm are found in it, also a few smaller ones, and these openings must be regarded as oscula. In the thicker, irregularly leaf- shaped specimens a few wide perpendicular canals are also often found, opening in the edge; but I am not quite sure, whether the question is here of real oscular canals, or they are secondary canals arisen by coalescing. In the membrane coating these canals, dermal spicules are found and also pore- shaped openings; this, however, does not exclude the fact that they may belong to the original canal system, and, on the other hand, in undamaged specimens their mouths are surrounded by the dermal membrane as a round, sharply bounded opening. I therefore regard it as probable that the question is of oscula, and the fact is then that the small oscula on the surfaces lead to the smaller, horizontal canals, while the oscula found in the edge are larger and lead to longer perpendicular canals which pass down through the thicker parts of the irregularly leaf-shaped sponge. The skeleton. The dermal skeleton, as mentioned above, consists chiefly of bundles of dermal spicules, which are spread in a somewhat peuicillate way and support the dermal membrane, and, but only to a slight degree, pierce it. This skeleton is otherwise little regular, the bundles are most frequently more or less recumbent, often quite so, and scattered spicules may also be found in the membrane; in some places the skeleton may be formed entirely of horizontal, scattered spicules, which seems especially to be the case in places where no pores are found. The ridges of the surface are often seen to be more spined, which is then owing to the fact that the spicules of the skeleton itself here project through the dermal membrane; I suppose, however, that this feature is often due to damaging. Tornotes are not found in the mem
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