PORIFERA. III. 



the layer of tissue outside on the axis is thin, but the skeleton is of the same construction, with 

 radiating fibres. The skeleton in the wall of the oscular cones is formed of a dense layer of tornotes 

 all parallel to the longitudinal direction of the cone; they are partly divided into bands or fibres; this 

 skeleton is formed in such a way that the fibres going to the surface continue out in the oscular cones 

 at the places, where oscula are found. On the outer side of the oscular cone there is found a layer 

 of acanthostyles, and further there are many chelse in the wall. This structure of the oscular cone 

 shows, that it is not formed of the dermal membrane solely. As a rule the spicular axis is very thick 

 and strong, it is thus in one of the larger specimens 2 mm thick below in the peduncle, and above, at 

 the upper end, 0-6 mm thick. The skeleton is constructed in the described way in the specimens where 

 it is regular, but a good deal of irregularity may occur, I think partly caused by the presence of the 

 inner cavities. Between the ordinary fibres some very thick ones may occur, which present themselves 

 as branchings of the axis; the fibres going towards the surface may be curved in different ways, as 

 they bend round about the cavities, and they may bend round to such a degree, that they do not go 

 upwards but downwards. Some of these irregularities are certainly due to the contraction, and I think 

 the skeleton would show more regularity, if it was examined in a sponge in a quite distended condition. - 

 Spongin is found in the spicular axis, especially below, towards the base, but the amount is only 

 slight, and I could not observe any spongin outside the axis. 



Spicula : a. Megasclera ; i. The skeletal spicules are tornota, they are straight or slightly, 

 and then as a rule somewhat irregularly, curved, they are slightly fusiform and have somewhat short, 

 sharply pointed ends; the length may vary a little in various individuals, it is 0-357 0-58 mm , and the 

 thickness may in all vary between 0-005 an< ^ o-oii mm , by far most frequently it lies between 0-007 anc * 

 o-oo8 mm . The tornotes sometimes show a quite slight tendency to become polytylote. The fully developed 

 tornotes have quite equal ends, but quite fine developmental stages were observed, and these were 

 styles; when they have grown a little older, they have still unequal ends, but they get equal-ended 

 already at an early stage. 2. The dermal spicules must be termed acanthostyli, as one end is 

 pointed, but the apex is short; sometimes, but rarely, the apex is indistinct or quite wanting, so that 

 the spicules are near to, or are really strongyles. They are more or less curved, and it is worthy of 

 note, that the curvature nearly always lies nearest to the rounded end; the spicules are distinctly 

 fusiform. The spinulation is dense and coarse, the spines have a length of about half the diameter 

 of the spicule. The spinulation may vary somewhat with regard to density and the size of the 

 spines and this is in relation to the variation of the spicule in size, in such a way, that the larger the 

 spicule is the more densely it is generally spined, and the larger are the spines. To be sure these 

 variations may generally be found in the same individual, but there may, however, be the difference 

 between the individuals that in some the smaller, in others the larger spicules are by far the most 

 numerous, in a single specimen the acanthostyles are on an average more diffusely spined than in 

 the others. The length of the acanthostyles is 0-119 0-196 mm and the thickness in the middle, the 

 spines not included, 0-005 o-oi4 mm . A number of developmental forms in different stages were present, 

 the finest of them being already distinctly and somewhat strongly spinulous; the developmental stages 

 are all distinctly monactinal. As said above the tornotes form the fibres, while the acanthostyles form 

 the dermal skeleton, but are also found in the interior of the body, especially between the fibres. 



