PORIFERA. III. 



spiculcs. Oscula few, lying on special papilla, pores on the summit of other papilla. The skeleton a 

 i/i a inly polyspicular, difftise and irregular reticulation. Spicula: megasclera: the skeletal spiculcs styli 

 OTJO 0-68 mm , the dermal spicules tylota 0-25 0-47 mm ; microsclcra one form, finely spinulous rhaphides 

 with unequal ends 0-05 j 0-50""*. 



Of this species we have a very rich material from the whole Ingolf territory. The individuals 

 may have a very different aspect, but as a rule they are characterized by having a greater or smaller 

 number of wart-shaped papillae. In the typical and fully developed shape the species is massive, more 

 or less roundish, lumpy and in greater or smaller extent attached to a substratum. From this roundish 

 shape the species may show many variations, it may be elongated and assume a somewhat erect 

 shape, and it may be club-shaped, lobate, compressed or more or less branched. The latter shape is no 

 doubt due however, at all events partly, to the fact, that it incrusts, or originally has incrusted, branched 

 Hydroids or Algae, but in this case it seems to be able to continue its growth out in free, branched 

 forms. The smallest and youngest specimens are incrusting and from this crust-shaped origin it may 

 then by and by grow up to the massive shape, but it may also persevere as a crust and as such 

 reach a considerable extent In our material it is found growing on stones, various Bryozoa, worm- 

 tubes, Algae e. g. Ptilota plumosa, the specimen on this is branched, and finally on a crab. The largest 

 specimen, which is of an elongated shape, has a length of about 4o ram ; a massive, tuberous specimen 

 is 30""" in diameter; the incrusting specimens are generally small, but may, as said, reach a greater 

 extent, up to 25 mm with a thickness not much over i mm . Topsent mentions and figures (1. c.) larger 

 specimens, up to an extent of 9=-, of typical massive shape. The colour (in spirit) is yellow or 

 whitish yellow. The consistency is of medium firmness and somewhat elastic. The surface is more 

 or less densely beset with papillae, otherwise it is, when examined with a lens, somewhat diffusely 

 hispid. In the larger, massive specimens the papillae are generally present in great numbers, and the 

 same is the case with the larger crusts; in the small incrustations the papillae may be few or indistinct. 

 The dermal membrane is a very solid and easily separable membrane; outermost it shows a thin, film- 

 like layer, which under the microscope is seen to be curled or folded. It would seem that this layer 

 in the living sponge is adhesive, as it generally shows adherent foreign particles such as diatoms in 

 great multitude. Oscula and pores: as mentioned the surface is more or less richly beset with papillae 

 which are specially well developed in the larger specimens, while they are less developed in the 

 small specimens. The papillae are conical in their lower part, the upper part being cylindrical. They 

 are seen from quite small warts up to a length of 4 mm ; they are compressed and have a breadth up to 

 1-5 mm . These papillae must be supposed to he partly oscular- and partly pore-papillae, the fact is, 

 that they show some difference. Some few of them are simply hollow and show an opening in the 

 summit, their wall is thin and supported by dermal spicules which are more or less distinctly arranged 

 as longitudinal bands; these papillae must accordingly be taken to be oscular-papillae. By far the most 

 of the papillae have another structure; they are hollow like the oscular-papillae, but from the wall spi- 

 cula fibres stretch into the lumen; these fibres may be branched upwards and terminate in the upper 

 surface of the papillae, which is thus supported by a number of spicular pillars. All the spicules in 

 these fibres are dermal spicules. The papillae show no opening at the summit. These papillae must 

 be supposed to be pore-papillae, and probably the pores are found at their ends. The pores I have 



