I22 PORIFKRA. II. 



shows great resemblance to Chalinina, especially to such forms of Pachychalina as the mentioned 

 ones. This resemblance is very great and is also found in the form of the megascleres, so that, 

 properly speaking, it is only by the occurrence of the characteristic chela that it can be decided, 

 whether a specimen belongs to a /doi/i/rod/clya-species, and confoundings have certainly now and then 

 taken place. In the form a frequent feature seems to be that a compression of the branches takes 

 place, and that larger or smaller portions of the lower part of the sponge form flat parts only branching 

 above or in the edge. This form seems to be rather constant in the species, and to stand somewhat 

 opposed to the common form of the Pac/iyc/iali/ia-species most resembling it. This difference is 

 especially found as a rule, but not always, between the present species and the Pac/iye/ial/na-species 

 (P. excelsa Schmidt) most common in the North-Sea. Of the species we have a rather considerable 

 material showing the variations of the form. A few specimens have a regular digitate form with only 

 a slight compression of the branches, especially in their lower part, while their upper end is cylindric 

 or almost eylindric. Several other specimens are less regular, with more compressed branches and 

 more expanded parts below, or the expanded parts become larger, and prevail almost over the in this 

 case shorter branches; finally we have one specimen, the branches of which are exceedingly flattened 

 and are lying in one plane, so that this specimen gets a very great breadth. The smallest and youngest 

 specimens are quite unbranched; and these small specimens are most frequently formed as a single 

 compressed branch or about oar-shaped, but irregularities may also occur at an early stage, so that 

 the smaller specimens form broad, flat, somewhat lobate bodies. The smallest one of all the specimens, 

 which is attached to a stalk of a Hydroid, is almost globular. Sometimes the lower part is more or 

 less marked off as a stalk, but the branching may also begin directly at the base. Most of the speci- 

 mens are torn off from the underlayer, of the others one is attached to the shell of a Modiola modiolus, 

 a few others partly to worm-tubes, partly to stalks of Laminaria. The number of branches is very 

 varying; the most richly branched specimen is above divided into about a dozen branches, but gener- 

 ally the number is smaller. The largest specimens are 34 cm high, and the regular, digitate branches 

 have an average breadth of about 25"""; then follows a series of specimens of decreasing sizes. The 

 largest of the smaller, unbranched specimens has a height of i3 cm , and the smallest one is 7-5 cm high. 

 The mentioned, still smaller, globular specimen has an extent of only 8 mm . The consistency is very 

 elastic, quite as in the C/iali/icr. The colour (in spirit) is generally light yellowish gray. The surface 

 is finely and densely, but quite short shaggy from the projecting ends of the fibres. The dermal 

 membrane is a thin and transparent film; it has no spicules, but rests on the skeleton beneath and is 

 pierced by the ends of the fibres. The pores are found in the dermal membrane, often so closely 

 placed that the membrane is reduced to a network; they are round or a little irregular and were 

 measured to a diameter of 0-03 — o-i2 mm . Oscula are circular or, more rarely, somewhat oval openings; 

 they are surrounded by a projecting, more or less pronounced, conical edge. They are directed some- 

 what upward, and consequently the projecting edge is higher on the lower side of the osculum. The 

 principal canal runs obliquely downward, but larger canals may frequently be seen to lead into the 

 principal one from different sides. Oscula vary in size from 6 mm quite down to i mm . They occur in 

 rather large numbers and are found from the very base of the sponge to the top of the branches. 

 Sometimes they may be said to be scattered, but most frequently their occurrence is limited to definite 



