PORIFERA. I. 65 



cnla: Mega sclera oxea. <ryH~(r4'j""" ; Microsclera toxa, rai/ier small, greatest length o-o6""'\ signiata 

 of a particular form ivilli the shaft bent into an angle 0-014 — o-o^""". 



This species is lengthily, but oftenest somewhat irregularly pyriform; the smaller specimens are 

 more roundish, a single one somewhat lobate. It must have been growing freely on the bottom, as 

 no place of attachment is found, but the sponge which is narrowing below, is here rounded, and ends 

 often with a larger or smaller knob, especially marked off. The largest specimen has a height of 60'""', 

 and a diameter in the middle of lyn""; then a series of specimens is found decreasing in size; the smallest 

 specimen has a height of 9""". The colour (in spirit) in most specimens is dirtily yellow, but in a few 

 it passes into a darker colour'). On account of the external rind-layer the consistency is rather firm. 

 The szirface is even and smooth, with here and there flat eminences and depressions. The sponge is 

 surrounded by a hard and firm dermal layer^ provided with spicules h'ing in every direction and ex- 

 ceedingly close-packed, but all parallel to the surface; this part that is marked off as a separate layer, 

 may be of a somewhat varying thickness, as will be more particuiarl)- mentioned below. Outermost a 

 thin dermal membrane is found, which, however, is not separable, and which I have only observed in 

 a few places, so that it seems for the greater part to be destroyed. In this membrane the pores are 

 found in the intervals left between the close-packed spicules; they are small, from o'cxdj"'™ up to 

 0-029"'"', or, but rarely, somewhat larger. With regard to oscitla only one is found, in the upper end 

 of the sponge; but I cannot give its structure and size, as the upper end is damaged in all the speci- 

 mens. The sponge is probably somewhat tapering above, or rather, as indicated by one of the least 

 damaged specimens shown in the figure PI. VI, fig. 5, it is here produced into a tube, in the end of 

 which the osculum is then found; the presence of such a thin-walled tube would explain the fact that 

 this fragile part has been broken off in all the specimens. Two oscular canals of equal width, running 

 side by side, and onh- separated by a thin membrane, lead in all the specimens from the upper end 

 towards the lower end of the sponge (PI. \T, fig. 8); in the largest specimen they have a width above 

 of 4— s™". Into these oscular canals the excurrent canals open; the\- have a rather regular course 

 running from the outside obliqueh" upward and inward towards the oscular canals and at the same 

 time converging to wider canals. 



The skeleton. As mentioned the sponge is surrounded by a hard and firm part marked off as 

 a dermal layer. The firmness of this layer is due to very closely packed spicules, lying in all direc- 

 tions in several layers, but parallel to the surface. The thickness may be somewhat varying, but is 

 o-reatest in the lower part of the sponge, and decreases upward; in the lower part it may be somewhat 

 more than i"""^. Where a knob-like lowermost part is especially marked off, this part consists almost com- 

 pleteh- of this skeletal tissue, which nia\- here reach a thickness of up to ^'^"'. When the dermal la>-er 

 in the lower part of the sponge is rather thick, it consists also of heterogenous layers, layers with 

 close-packed spicules parallel to the surface alternating with layers, in which the spicules are arranged 

 in a more netlike manner, and are not parallel to the surface. The other skeleton has a rather pecu- 

 liar, lamellar structure, consisting of thin lamellje, more or less parallel to the surface; these lamellae 

 consist of close-packed spicules parallel to the surface, as in the dermal la\er; between the lamellte a 



') A couple of the specimens are quite grayish black; this colour I take, however, to be due to colouring by other 

 sponges, together with which they have been lying in spirit. 



The Ingolf-Expedction. Vr. i. 9 



