PORIFERA. II. 



r 59 



in many places, especially, perhaps, where pore-sieves are found, there are penicillate bundles of dermal 

 spicules supporting the dermal membrane. Along the edge of the pore areas they may become short 

 fibres branching into the area among the pores, and then they are more or less, often quite recumbent 

 in the membrane. They do not reach quite into the middle part of the area, and here the membrane 

 is consequently without spicules. In other places dermal spicules are only found scattered in the skin, 

 both singly and in bundles. In these last places the membrane is resting on the main skeleton below, 

 the spicules of which project, and also where projecting bundles of dermal spicules are found, projecting 

 skeletal spicules are seen in them The main skeleton, by far the greatest part of it, is a polyspicular, 

 irregular, and rather close network. No distinction can be made between primary fibres and secondary 

 ones; the meshes are triangular or quadrangular or quite irregular. The fibres, as mentioned, are most 

 frequently polyspicular, but the meshes are also here and there bounded by single spicules. In the 

 leaf-shaped specimens longer fibres may be found running in the longitudinal direction of the leaf, 

 but else without any regularity. Otherwise, longer fibres are not found in the skeleton, and in the 

 leaf-shaped specimens no fibres are found passing perpendicularly to the surface or spreading towards 

 the surface in a penicillate way. Spongin is found in the nodes of the skeleton, but to a very slight 

 amount; moreover, it is white and clear, and consequently only to be seen with difficulty. 



Spicula: a. Mcgasclera. i. The skeletal spicules are styli; they have a curve, most fre- 

 quently a rather slight one, nearest to the rounded end, while the other part of the needle is straight 

 or almost straight; more rarely the curve is more even through the whole length of the spicule, or it 

 is irregular. The point is even and middle long. The styli may be slightly spined or smooth. In the 

 spined oues the spines are only found in a short part at the upper end, and the spines are so small 

 as only to make the surface finely gritty; a few scattered, also very small spines are often found 

 farther down the styli. This slight spinulation may become quite minimal, and it may entirely dis- 

 appear, so that the style becomes smooth. In the material in hand there are no instances of smooth 

 and spined styli occurring in equal numbers; either all the styli are spined, and smooth ones occur 

 only as exceptions, or the case is the reverse. The length varies from 0-29 — o-40 mm , the smallest length 

 occurring more rarely, and the thickness is ca. cron — o-oiy mm , the longest ones being far from always 

 the thickest ones. Some finer to quite fine developmental forms occur; they seem to be finely and 

 dispersedly gritty from spines almost through their whole length, and this not only in the specimens 

 that have almost no smooth styli, but also in those with almost exclusively smooth styli. The 

 finest stages observed had a length of o-26 mm with a thickness of only crooi4 mm . 2. The dermal 

 spicules are tornota; they are straight, only rarely a little irregularly curved. Their two ends 

 are not equal, one is a little thicker, and it is rounded with a quite slight mucro, the other, on the 

 other hand, forms a rather short point, so that the needle might be interpreted as a short-pointed 

 style 1 ). The length is 0-20 — o-268 ,nra , and the thickness 0-003 — o-oo5 mra . The finer these spicules are, 

 the more marked is the difference between their two ends, and I have seen quite few fine develop- 

 mental forms with the thin end rather long pointed, b. Microsclera ; these are of two forms, chelae 

 arcuatae and sigmata. 1. The chelae have a curved shaft with the strongest curve in the middle; 



*S' 



x ) The several compound terms (toniostrongyla etc.), which may often be used advantageously, are here, as often else, 

 not sufficiently characteristic; the name that would best describe the present form should, I suppose, be «oxytoruote». 



