PORIFERA. III. 17 



and they have a diameter of 0-036 o-io mm . The circulation of the water-current is then the same, 

 as was mentioned under H. appendiculatum ; there is also here a space below the dermal rind, and 

 in a section of the inner body parallel with the surface the small, round incurrent openings to the 

 canals are, under the microscope, seen lying very closely. 



The skeleton. The dermal skeleton; the skeleton of the dermal layer is formed of close-lying, 

 tangential spicules, which lie in several layers and form a solid and protective rind. The greatest 

 part of the spicules lie parallel to each other in a direction which goes more or less distinctly 

 circularly round the sponge, thus the spicules lie at right angles to the longitudinal direction of 

 the body of the sponge; at the same time they are, in the environs of the fistulae, arranged ring-like 

 around the bases of these. When the surface is undamaged, there is outermost a layer of more loose- 

 lying spicules which lie crossing each other in all directions; between the regularly arranged spicules 

 of the layer there are spicules placed at right angles to the others. A section through the layer 

 parallel to the ring-like arranged spicules will thus show entire spicules lying parallel to each other 

 on the inside, and cut, irregular!}' lying spicules on the outside. The spined strongyla occur especially 

 at the outer side. The skeleton in the fistulae is ring-like arranged at the base, but outwards it 

 passes soon into an irregular skeleton with spicules intercrossing in all directions; in the oscular 

 fistulas the spicules are in the conical summit arranged parallel to the longitudinal direction and with one 

 end towards the oscular opening; in the pore-fistulse there is at the end an irregular reticulation, in 

 the meshes of which the pores lie. The skeleton of the inner body is difficult to get a clear idea of 

 on account of the brittleness and contracted condition of the tissue, and also on account of its very- 

 dark colour. It is however not regular as in the preceding species, but seems only to consist of 

 scattered spicules; at the surface they are present in greatest numbers while they are much scattered 

 in the interior, and they are on the whole not numerous. Spongin is not present in the skeleton. 



Spicula: a. Megasclera; these are of two forms, smooth strongyla and acanthostrongyla. i. The 

 smooth strongyla are straight, more rarely quite slightly curved, they are thickest in the middle 

 and taper slightly towards the rounded ends, which latter sometimes may be quite slightly swollen. 

 The ends are very finely spinulous on the rounded part; the spinulation may be very little apparent 

 but is generally rather distinct, it is most obvious on the smaller spicules. The length varies much, 

 from 0*24 mm and up to ro2 mm , and the thickness is 0-008 0-02 i mm . In the dermal layer strongyla of 

 all sizes are found, the larger are present in greatest numbers, in the inner body on the contrary only 

 the smaller forms are found, up to a length of 0-47 mm , but at the surface of the inner body they are 

 somewhat larger up to 0-7 1""". 2. The acanthostrongyla or spined strongyla are relatively 

 short and thick; they are generally sligtly curved, coarsely spined strongyla, sometimes each end 

 terminates in a point, but as this is not, or only very slightly, larger than the other spines, it must 

 be taken as such and the spicule must be termed a strongyle. The length is about 0-12 0-238 mm , the 

 shortest forms occur most rarely, the thickness is oxm o-oi7 mm . The acauthostrongyla occur both in 

 the dermal layer and the inner body scattered between the other spicules; in the dermal layer they 

 are especially present towards the outer side. Microsclera are not present. 



Locality: This is the same as for the preceding species, viz. station 78, 60 37' Lat N., 27 52' 

 Long. W., depth 799 fathoms. 



The Ingolf-Expcilition. VI. 3. 3 



