PORIFERA. II. 59 



specimen (from the Kara Sea) has a length of ca. 135'""', the stalk is 26"™ long, the greatest thickness 

 is 7 mm , and the stalk is ca. 2 mm thick. Then we have specimens of all sizes downward, the smallest 

 specimen is 15™°" high. The mentioned leaf-shaped specimen has a height of jj™™, and a breadth of 

 ca. 70™'", its stalk is only \7> mm long. The consistency of the upper part of the sponge is softer than 

 in the preceding species, the stalk is hard. The colour (in spirit) is whitish gray to whitish yellow. 

 The surface, apart from the nature described above, must be said to be smooth, only in the ends of 

 the lateral branches bundles of spicules project. 1 11 the specimens in which no lateral branches pro- 

 perly so called are found, but only longitudinal ridges and irregular projections, spicules project through 

 these, and thus these individuals get a more shaggy appearance. Under the microscope also other 

 parts of the surface may appear shaggy from the projecting chela;. The upper part of the stalk is 

 smooth, but it becomes shaggy towards the base. A dermal membrane ma}- distinctly be observed, 

 and is easily isolated; it is thin and transparent and highly filled with chelse, on the other hand there 

 is no dermal skeleton proper, but the membrane rests on the skeleton below, and when it is isolated, 

 needles may be seen scattered in it. Pores have not been observed in the dermal membrane. Oscula: 

 the mentioned lateral branches act, no doubt, as oscula; the fact is, that these branches are not solid, 

 but are chiefly formed by the dermal membrane, which is here supported by spicules parallel to the 

 longitudinal axis of the branches. If a branch is cut off it is seen to be hollow, and leaves a hole; 

 on the other hand, an osculum is not distinctly seen at the point of the branch, as the spicules are here 

 closer joined. As the branches are very numerous, and as pores have not been observed, it might be 

 supposed that also the inhalent system was connected with the branches; it is, however, more prob- 

 able that the pores are closed. 



The skeleton. The skeleton of the axis consists of close-lying spicules parallel to the longitu- 

 dinal direction. The axis, however, is not quite compact, the spicules being collected into close-lying 

 fibres; in the interstices an irregular reticulation of spicules is found, which spicules are placed obli- 

 quelv to, or across of, the longitudinal direction; sometimes, however, this feature is little prominent, 

 and then the axis is more compact. It continues from the stalk up through the sponge, quite to its 

 uppermost end, and it keeps about the same thickness. The outer skeleton, which supports the upper 

 part, consists of a quite irregular net-work of spicula-bundles and scattered spicules, with short fibres 

 here and there. As mentioned, the lateral branches are supported by spicules apparently forming a 

 fibre, but really only supporting the wall of the branch; these spicules do not reach to the axis, but 

 pass only into the other skeletal net. In the lower part of the stalk, where it is shaggy, spicules are 

 woven into it, projecting more or less horizontally, and over the surface. A coating with special spi- 

 cules is not found. In the mentioned leaf-shaped specimen the skeletal structure has been modified 

 in an interesting manner; the short stalk continues as such only a short way into the leaf, and then 

 it is lost. It does not cease, however, but is, as it were, spread in the plate, rather close-lying fibres, 

 radiating towards the edge, running through the plate; these fibres correspond to those of the axis, 

 and they are, like those, connected by spicules and spicula-bundles, which are placed transversely or 

 obliquelv in the interstices. This whole structure forms a thin skeletal plate in the middle of the leaf- 

 shaped part, and on both sides is found a tissue with a skeleton constructed in the same manner as 

 the skeleton outside the axis in the other individuals. In the axis the spicules are united by a rather 



s* 



