PORIFERA. II. 25 



small oscular cones. The skeleton consists of polyspicular fibres branching up through the sponge. The 

 spicules piercing the dermal membrane are smaller than the other spicules of the skeleton. Spicula: 

 Megasclera styli or subtylos/yli. sometimes with the upper end formed like a handle; the styli of the 

 skeleton o-jjy—o-ji 5""". those of the dermal membrane o-j — 0-5"""; microsclera of three forms, anisochela 

 palmetto- 0-025 — 0-092""". the large ones frequently in rosettes ; sigmata 0-0/7 — 0-027"""; rhaphides in 

 trichodragmata 0-043 — 0-085""". 



Mycale placoides has been rather carefully described by Carter in the place quoted, and he 

 has rendered an account of most of the characteristic structural features. On account of the great 

 resemblance between this species and the following one, it will, however, be of importance that a full 

 description is given of both of them. The form of the sponge seems to be somewhat varying, but is 

 always erect; the hitherto known specimens, mentioned and figured by Carter and Top sent, are 

 erect and more or less cylindrical or club-shaped, being somewhat narrowed below. All the specimens 

 before me are more or less damaged, but with regard to the form it may, however, be decided from 

 them that the sponge, besides the mentioned form of which I have some specimens, may also be more 

 or less compressed, or be drawn out into some broad and irregular lobes reaching through the whole 

 length. The specimens mentioned by Carter and Top sent had a height of 6-5 — 9 c,n . Most of the 

 specimens before me are considerably larger, the club-shaped specimens thus up to a height of 17"". 

 The largest specimen consists of some fragments which were stated by the collector, Dr. Morten sen, 

 to have belonged to one specimen. Its form has been somewhat compressed, presumably as a thick 

 leaf. It has been a very large specimen; but the lower part wanting, and, I suppose, to a rather great 

 extent, the height cannot be given, but the breadth above has been ca. 30 cm , and the thickness 5—6™. 

 The consistency is soft and not elastic, and therefore the sponge, in spite of the thick fibres, is rather 

 fragile. The mentioned largest specimen is stated to have been very slimy, when it was taken up in 

 the trawl. The colour (in spirit) is generally whitish yellow. The surface, as is well known, has a 

 characteristic appearance being completely furrowed by a large number of sinuous or branching fur- 

 rows that may be arranged in very different ways. The parts between the furrows are finely shaggy 

 from projecting spicules, while the furrows are smooth. The dermal membrane is thin without any 

 particular skeleton; it is supported by the ends of the fibres, the spicules of which are spread in a 

 penicillate way, and project a little through it, and it is stretched over the furrows of the surface. 

 Pores and oscula. As has been very well described by Carter, the mentioned furrows in the 

 surface are pore areas. They may show a very different arrangement, being sinuous and branched in 

 many different ways. They may be placed rather near to, or more far from, each other, and conse- 

 quently the parts between them may be larger or smaller plates, or may be reduced to projecting 

 knobs or rather long keels. Then the furrows may be quite narrow, almost quite closed, or broad 

 and flat; this latter feature is probably mostly caused by the greater or lesser contraction of the skin 

 in the place in question. The pores are found in the membrane that is stretched in the furrow, most 

 frequently very close-set, so that the membrane resembles a sieve. Of the strings of tissue separating the 

 pores, some are generally thicker principal strings, between which the pores are placed more or less 

 arranged in series. These strings, which may be distinctly seen by means of a magnifying glass, pass 



The Ingolf-Expedition VI. 2. 4 



