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



chambers, while the outer trabecular framework either entirely fills the space between 

 the chambers and the outer skin, or is perforated by the subdermal lacunae and afferent 

 canals. 



The name of the genus Twgeria is formed from the family name of my wife, " Taeger." 



Genus 2. Walteria, n. gen. 



Walteria jlemmingii, n. sp. (PI. IX.; PL X.; PL XL figs. 4-6). 



The fragment of a hitherto unknown Hexactinellid, which is very faithfully 

 represented in its natural size on PL IX., was collected in the Pacific to the north of the 

 Kermadec Islands (Station I^Oa, lat. 29° 45' S., long. 178° 11' W.), from a depth 

 of 630 fathoms, on volcanic mud. The sponge apjiears to be broken across the middle, 

 and to have had about double the length of the fragment preserved, which is 15 cm. 

 long by 8 cm. broad, becoming narrowed towards its extremity into a conical funnel- 

 shaped tube only 6 mm. in width. Since the terminal portion is also broken off at this 

 place it is impossible to determine whether w^e have before us the inferior extremity by 

 which the sponge was fixed or the free upper end. 



The thin wall of the tube consists of a framework wath strands of varied strength, 

 seldom more than 1 mm. in thickness, and surrounding polygonal meshes of very diverse 

 size and irregular form, which may attain the size of 1 cm. It is only towards the 

 narrowed funnel-like end that the strands arrange themselves in a system of somewhat 

 converging longitudinal and transverse bands of fibres, which come to lie closer and 

 closer to one another, forming quadrangular meshes, \\'hich are only crossed by small 

 secondary beams. Here and there in the expanded main portion of the sponge longitudinal 

 and transverse beams may also be recognised. Most of the beams in the lattice-like 

 network are not smooth, but are beset with small knobs which project externally, 

 and which occur sometimes isolated, sometimes in grouped arrangement. Even on 

 examination with the naked eye, but more obviously by employing a lens or the 

 microscope, the network strands may be seen to be supported by a firmly united sUiceous 

 framework, which is covered by a distinct and strongly-developed soft skin. The latter 

 becomes elevated into numerous small short tubes which project obliquely or at right 

 angles to the surface, and are each tenanted by the hydranth of a commensal hydroid 

 poly|5e. While the hydrophyton extends into the deeper layer of the rind, the shortly- 

 stalked or sessile hydranths project transversely outwards (PL XI. fig. 4). There can 

 be no doubt that the hydranth, by its simple presence and especially by the continual 

 stimulus exercised on the surrounding sponge substance by its expansion and 

 contraction, has caused the formation of the projecting tubes. I have not observed 

 anything of the nature of a perisarc. The hydroids seem to be entirely naked, and lie 



