REPORT ON THE HEXACTINELLIDA. 205 



form of the body as seen in the second specimen, which is comparatively well preserved, 

 but also destitute of basal tuft, is represented in natural size in PI. XXIX. fig. 1. We 

 have here an inverted conical form, with slightly bulging sides, and a broad upper 

 end not transversely truncated, Imt depressed in funnel-like fashion, and covered by a 

 narrow-meshed delicate network, while the external lateral surface of the body is enveloped 

 by a delicate dermal sieve-work — the dermal membrane, through which the more or less 

 regularly distributed large inhalent canals of the afierent system are seen as dark 

 spots (PI. XXIX. fig. 1). On the upper external margin, which projects as a sharply 

 defined ring, there is a continuous fringe of marginal spicules. On the lower, somewhat 

 incurved end, lies a round gaping opening, about 6 mm. in width. This leads into a 

 straight canal, and there can be no doubt that it represents the position of the torn off 

 basal tuft. 



The third much smaller specimen, with a well-preserved tuft of basal spicules, 

 as also figured by Wyville Thomson, differs essentially in external form from the 

 above specimens. The body is not conical but oval, with truncated superior, and 

 somewhat narrowed inferior extremity. The structure, however, agrees so exactly with 

 that of both the other specimens, that one can have no hesitation in acknowledging the 

 correctness of Wyville Thomson's reference of this form to the same species, Hyalonema 

 toxeres. The specimen is unfortunately not well preserved, especially towards the upper 

 end. On the middle of the upper terminal surface the conus projects, and from it four 

 cruciate longitudinal septa with smooth, convex, superior margin extend through the 

 central space to the lateral wall into whieh they pass. The four cruciate cavities 

 thus formed are continued downwards and sideways into the efferent lacunar passages 

 of the parenchyma. Close beneath the narrowed inferior portion with the smaU basal 

 tuft thei'e is a ring of a few Palytlioa individuals (PI. XXIX. fig. 4). 



Microscopic examination of the flinty spicules shows the intimate similarity of all the 

 three specimens, and the few variations which are present are referable to diflerences in 

 age and individual characteristics. 



In the parenchyma, besides the familiar regular medium-sized oxyhexacts, and 

 numerous straight or slightly bent, weakly developed diacts with or without central 

 swellings or knobs, especially remarkable and characteristic diacts occur. These are thick 

 and spindle-shaped, curved or somewhat bent, with rounded terminal points, and without 

 central swelling or tubercles. These bent needles measure 3 to 8 mm. in length, and 

 exhibit in the middle a thickness of 0"3 to 0'4 mm. The concentric lamination is very 

 distinctly seen, and on the outer end the relation of the various layers of growth is 

 often most beautifully demonstrable (PI. XXIX. fig. 11). The distribution of these 

 strong, bent needles in the parenchyma seems to me quite irregular. I have not observed 

 their special abundance in any one region, nor on the other hand any definite disposition. 

 They frequently occur parallel to the skin near the external surfocc, but also in 



