PORIFERA. III. 



Reniera, being caused by the close-lying, circular openings of the incurrent canals which shine through 

 the thin, transparent outer layer, in which there are fine pores leading to the canals. The poriferous 

 fistulas probably do not lead into canals, but are in connection with the space below the dermal 

 layer; perhaps it is these fistula; whose diaphragm shows no opening in the centre. The course of 

 the water-current will then probably be: it passes in through the poriferous fistulse into the space 

 below the dermal layer, from here through the pore-shaped openings on the surface of the inner body 

 and into the canal system, then in due course passing into the larger canals and finally out through 

 the oscular fistulas. 



The skeleton. The dermal skeleton; the outer rind is highly provided with spicules lying 

 very closely and in several layers, parallel to the surface; the spicules are not scattered, but arranged 

 somewhat circularly round the bases of the fistulse, as is already distinctly visible with a lens; on 

 the inner side of the rind there are some spicules which lie singly and rectangularly to the direction 

 of the other spicules, and thus more or less radiating in relation to the circlets. In the fistulae the 

 ring-like arrangement of the spicules is retained, which is the cause why the fistulae are very easily 

 broken; some fine fibres, consisting of few spicules, run lengthwise out through the fistulas, lying on 

 the inside of the wall, and continue from the base to the end of the fistulse in longitudinal direction; 

 these fibres do not belong to the dermal skeleton, in so far as they are not found in the dermal 

 layer of the body, on the contrary they issue from the inner body, and they are probably of 

 importance in attaching it, and thus it is that the inner body, as said above, is attached only at the 

 bases of the fistulse. In the ends of the fistulas the dermal skeleton gets more scattered, and in the 

 oscular fistulse the spicules are here irregularly scattered, crossing each other, while in the poriferous 

 fistulas the skeleton outwards first becomes somewhat scattered, but outermost forms a reticulation. 

 The main skeleton or the skeleton of the inner body: In the inner body some fine fibres are found, 

 but they have no regular course and form no reticulation; they seem mainly to run in directions 

 parallel to the surface. At the very surface of the inner body such fibres are found numerously, 

 running just below the surface and parallel with this, and they show a definite arrangement. They 

 run together at the bases of the fistulas and continue, as said before, out in the fistulse; as they 

 radiate from the base of the fistulse out in the surface, they become in the larger part of this 

 parallel with each other, but at places where the systems belonging to different fistulse meet, the 

 fibres run in different directions. Transverse fibres are not found, and thus there is no reticulation 

 formed. The fibres are somewhat loose, they have an average thickness of 0-05 mm , and the distance 

 between them is generally 0-15- 0-25 mm . -- It was said above, that the inner body lies loose in the 

 cavity of the dermal layer; as the fibres mentioned continue from the fistulae inwards and form 

 a carpentry along the surface of the inner body, this latter is in reality kept in its place by this 

 carpentry, otherwise lying freely in the cavity and only attached at the bases of the fistulse. Spongin 

 was not observed, neither in the inner skeleton nor in the dermal skeleton. Carter has not seen 

 the construction of the skeleton of the inner body; in his material the inner body has probably been 

 destroyed. Both in the dermal layer and in the inner body many foreign particles are imbedded, 

 especially Globigerinae. 



Spicula: a. Megasclera; these are only of one form, tylotes, but with some single intermediates 



The Ingolf-Expedition. VI. 3. 2 



