12 



PORIFERA. III. 



be more or less roundish or of a more irregular, sometimes somewhat erect shape. The largest 

 specimen in my material has a greatest extent of fully 3o mm ; it has two spout-shaped tubes and a 

 height of i8 mm from the base to the end of the tubes; the smallest specimen has an extent of about 

 5 mm . My specimens are attached to stones with a broad base, one is growing on a crab. The con- 

 sistency of the outer layer is firm and hard; the inner body is brittle; in all specimens the latter is 

 contracted and forms only a clump at the base of the bladder, and the same can be seen to have 

 been the case with the specimen figured by Schmidt. The colour (in spirit) is whitish. The 

 surface is smooth. Outermost is found the dermal layer, it is constructed mainly in the same way 

 as in the preceding spedes, and has a thickness of about 0-15 m ' D . Pores and oscula: My specimens 

 are all in a rather bad condition, so that the examination of the arrangement of the pores and oscula, 

 which would seem to be rather interesting, may be somewhat deficient, and as the inner body is 

 destroyed, we get from this no information about the canal system. Only the largest specimen is in 

 such a condition, that it gives some information about pores and oscula, and I think, that the structures 

 shown by this specimen are typical for the species, especially as the figure given by Schmidt seems 

 to show a quite similar structure. This specimen has, as said, two tubular or conical spouts, formed 

 of the dermal layer; these spouts have a shape as shown on PI. I figs. 12 13. The osculum is found 

 as a simple opening at the summit of the conical end part of the spout; the spicules of the dermal 

 layer lie parallel with each other here and with one end towards the oscular opening. On the side 

 of the tube is found a circular opening, surrounded by a low, projecting wall; the opening is covered 

 by the poriferous membrane. The skeleton of the dermal layer forms here a reticulation, as fibres go 

 inwards from the edge of the wall and support the membrane. The pores are numerously present 

 in the membrane, they are small, of an average diameter of o - o6 mm . 



The skeleton. The dermal skeleton; as in the preceding species we find outermost a firm 

 dermal rind which, however, in the present species is somewhat thinner and less solid than in appcn- 

 diculatum. It is provided with close-lying spicules parallel to the surface, and the spicules lie in 

 several layers; they are mainly more or less parallel to each other, but there are also, especially 

 on both surfaces of the layer, spicules present, both in bundles and lying singly, which are scattered 

 and cross the other spicules in all directions. The main skeleton; on account of the condition of the 

 material I have only been able to examine the skeleton of the inner body somewhat incompletely, it 

 seems however to be constructed quite as in appendiculatum ; in the interior there are fibres and 

 bundles, and at the surface there are parallel fibres without transverse fibres; the fibres were measured 

 to a thickness of 0-08 n " n with a distance between them of 0-29 mm . Spongin is not present in the 

 skeleton. 



Spicula. a. Megasclera; these are of one form, strongyles, sometimes approaching to subtylotes; 

 they are slightly curved, generally irregularly and most frequently doubly. They are fusiform, tapering 

 somewhat towards each end. The length when all examined specimens are considered is 0-50 0-89 mm , 

 and the thickness crooS o'O2O mm , but in the single individuals they do not vary so much, as examples 

 may be given 0*50 O74 mm with thickness of 0-008 o-oi5"" n and 0-62 0-89 " Im with thickness of o-oio 

 o-o2O mm . Fine developmental stages are seen singly, the finest are monactinal. b. Microsclcra; these 

 are of two forms, chelse arcuate and trichodragmata. i. The chelae arcuatse are of the common shape, 



