112 THE VOYAGE OF H.M.S. CHALLENGER. 



usually without any, or with only a very slight terminal swelling, and indeed, as a rule, ends 

 in a usually conical, roughened point. The length of the distal and proximal radial rays 

 varies greatly. The tangentials measure, on an average, 0"2 to 0'3 mm. in length, and 

 the distals are not unfrequently of the same size, but the latter may in some situations, 

 e.g., near the lower end of the body, attain more than double the length of the former. 

 The proximal ray exhibits a similar variability, measuring sometimes only O'l mm. in 

 length, and in other cases 0"4 to 0'5 or more, while in thickness it always falls consider- 

 ably below that of the distal. 



Here and there, on the external surfece, I found simple cruciform tetracts, with 

 smooth knobbed rays, pointed at the extremity (PI. LXX. fig. 10). The fact that, 

 for the most part, only a few dermalia were to be found on the external surface, is 

 probably to be traced to the injuries which the sponge seems to have suffered by 

 attrition. I found these dermal hexacts most abundantly and in best preservation at 

 the pointed basal extremity of the body, just above the origin of the stalk. They were 

 also abundant, though somewhat displaced, in the deep folds of the already mentioned 

 plicated side of the body, which, if flattened out, would form part of the external 

 surface. 



The stalk is chiefly composed of very long needles of various thickness, closely 

 arranged, parallel to the longitudinal axis, and, especially in the inferior portion, 

 frequently bound together by transverse synapticula (PI. LXX. fig. 9). On the external 

 surface, between the longitudinally disposed diacts, I found forms the same as those 

 above described as parenchymalia, as well as similar hexacts with club-shaped distal 

 rays, and simple cruciform tetracts, somewhat bent towards the surface. 



I am not in a position to report so definitely as to the gastral skeletal elements, since 

 I was not able to study them in their natural disposition. In the interior of the body, 

 in the numerous septa, hexacts and pentacts occur in abundance, with somewhat long, 

 smooth rays, which end in slightly club-shaped thickenings ; and it seems to me 

 probable that these function as gastralia, though I was unfortunately unable definitely 

 to determine their disposition. 



It is clear that this curious form, obtained from the depths of the South Pacific, at a 

 great distance from land, must occupy a peculiar position in the system of the Sponges. 

 On the one hand, the character of the hexact dermalia with their diverging distal rays 

 would suggest an alliance with the family of the Euplectellidse, in which, further, 

 such remarkable twisted oxydiacts alone occur (in Rhahdoplectella tintinnus, PI. XII. 

 fig. 11); while, on the other hand, all the microscopic characters of the body, and 

 the sharply defined, long, narrow stalk indicate a closer resemblance to such forms as 

 Crateromorpha, Aulochonc, and especially Caulocaly.v (PL LXIX.), to which we shall 

 have again to refer in detail. 



