„. PORIFERA. I. 



94 



network'). Of spicules the skin has only microsclera, viz. rhaphides of two sizes, especially occurring 

 in bundles, but without any order; in some places especially the long ones are seen, in others the 

 short ones; where pores are seen, the bundles of rhaphides, especially the short ones, seem to be re- 

 stricted to the strings between the thin-skinned pore fields, while long rhajDhides are seen scattered 

 singly also over the pore fields. Further sigmata of two sizes are found in the skin, of which the 

 larger ones are foiind rather sparingly in most places, while the smaller are everywhere abundant; 

 finally commata are also found abundantly. Osciila and pores: As before said, the pores are found in 

 the thin-skinned pore fields to a number of about ten in each field; they were measured of a size of 

 0-029 — '^^- o'la""". Where the skin was kept, here and tliere some circular openings were found of a 

 diameter of 15 — 2"'", which openings I take to be oscula. 



The skeleton is constructed in a quite similar way as in the preceding .species. It consists of 

 polyspicular fibres issuing at the base, and running up through the sponge. The fibres are thickest 

 at the base, and reach here a thickness of i — j-^mm; jn their branching upward the)' become somewhat 

 thinner, and at the same time they become more richly branched. In a radial longitudinal section the 

 more or less parallel or somewhat diverging longitudinal fibres are distinctly seen, thus being the 

 principal fibres; they are connected b}' numerous transverse anastomoses. Outward towards each side 

 the fibres send off branches supporting and piercing the dermal membrane (PI. VII, fig. 6). In the 

 tangential direction the fibres diverge and branch somewhat more, on account of the fan-shaped or 

 calicular form of the sponge. The spicules of the fibres are cemented by a distinct, but clear mass of 

 spongin, which is most copious towards the base of the sponge, and which seems to coat the fibres 

 entirely, although only with an exceedingh- thin layer. 



Spiciiln: a. Alcgaselera are styli, more or less, sometimes somewhat irregularly, curved; they 

 have a long tapering point, of which, however, the outermost end is shortly pointed. The length 

 varies from 075 — 1-56"'"; most frequently it is between i — 1-25""". The thickness is between about 

 0-024 — 0-036"™; generally the length and thickness are in proportion to each other, although it is not 

 always the case. Styli with a more or less broadly rounded point are rather frequenth- seen. Con- 

 siderably finer needles which may be regarded as developmental forms, occur in small numbers. 



Also in this species we find in the la\er touching the place of attachment irregularly formed 

 spicules of other dimensions than the other ones. 



b. Microsclera: i. Sigmata of two sizes; the large sigmata have a peculiar form, being highly 

 curved, and the curve is most frequently sharpest in the middle of the shaft, while the piece between 

 the curve and the hook-shaped end may be more or less straight; the ends are finely pointed and 

 recurved in a .sharply hook-shaped way. These sigmata are almost always contort, most frequently 

 abotit a quarter of a turn, but as well with regard to this feature, as upon the whole with regard to 

 form, they may be somewhat varying. Their length, which is, of course, somewhat dependent on the 

 degree of curving, is 0-08 — 0-107""", the thickness varies from 0-002 — 0-003""". Q»ite fine forms, deve- 

 lopmental phases, of the same length as the others, are also found. The.se sigmata are seen both 



') In these latter places no pores have been observed ; it is possible that the mentioned structvire of the skin is only 

 found in the places provided with pores, and it is also possible that pores are onl)- found in certain places and oscula in 

 others, but the material in hand has not been sufficient to enable me more particularly to elucidate this question. 



