164 



POR1FERA. II. 



The dermal spicules project only very little through the membrane, so that the surface is only very 

 slightly shaggy. The main skeleton is a rather close, but irregular reticulation. It is mostly poly- 

 spicular; fibres may be found running chiefly upwards or towards the surface. They may be somewhat 

 different with regard to their number of spicules alongside, but most frequently they have but few 

 spicules, and they are rather loose. Coherent transverse fibres are not formed, but are only represented 

 by single spicules or spicula-bundles. These transverse spicules are placed rather irregularly, and so the 

 net of meshes is upon the whole irregular. Frequently longer fibres are not found, but the skeleton 

 forms a quite irregular network of a somewhat diffuse character. The meshes are then irregular, also 

 often triangular; in this case the network is often more unispicular, so that the whole may convey an 

 impression of being quite diffuse with scattered, mostly single spicules without any formation of a 

 distinct network. A distinctly observable, but rather slight amount of spongin is found in the nodes 

 of the skeleton. 



Spicitla: a. Megasclera. 1. The skeletal spicules are styli; they are slightly and dispersedly 

 spined, sometimes quite smooth. They are most frequently slightly curved, sometimes a little more or 

 irregularly so; the point is rather short. The spinulation may be very varying; at most the styli 

 are dispersedly spined, and then all transitions are found to quite smooth ones. Then differences in 

 this respect may be found in different individuals; in some spined styli are almost exclusively found, 

 and of these most belong to the most highly spined ones, while quite smooth ones are only rarely 

 seen ; in other individuals the smooth styli are predominant, and the spined ones are then very slightly 

 spined. Their length varies from 0-35 — o - 50 mm and the thickness from o - oo8 — croi4 mm . There may be 

 some difference with regard to the length in different individuals; in the material in hand the fact 

 seems to be that in individuals where the spined styli are predominant, they attain a little greater 

 length than in individuals with predominant smooth styli. Also the thickness may show a little 

 difference in the different individuals, a few ones especially having frequently thinner styli than the 

 others. 2. The dermal spicules are tornota or tornostrongyla; sometimes one or both ends are a 

 little swollen, so that they approach tylota or tylotornota. They are straight, more rarely they may 

 be somewhat irregularly curved. Their length varies from o - 20— 0'2o, inm and the thickness from ca. 

 0-0035 — o , oo57 nim . Some difference may be found in different individuals, so that in some the dermal 

 spicules are upon the whole a little longer than in others. As mentioned, there is most frequently a 

 little difference between the two ends, one being a little more swollen and especially a little more 

 rounded than the other. A few developmental forms were seen, which were quite monactinal with 

 the thin end pointed. In a single individual almost all the dermal spicules had ends a little 

 swollen, and these subtylota had not rarely uniform or almost uniform ends. b. Microsclcra. These 

 are chelae arcuatse, some peculiar, very small chelse, and sigmata. 1. The chelae arcuatse have 

 a regularly curved shaft; the tooth is elliptical and rather long, and the alae, of the same length 

 as the tooth, are rather narrow and therefore tooth-like; the chelse, therefore, are very similar to 

 ancorae, and by a superficial examination they may be confounded with ancorae, but by a closer exa- 

 mination they are seen to be chelae. This chela varies much in size, its length is o - oi8 — o-044 mm , and 

 the thickness of the shaft is 0-0018 — o - oo4 mm . The largest sizes are less frequent. 2. The small 



