Mr. H. J. Carter on new Sponges. 435 



Fig. 9. Tethya a'animn, Johnston, attaclied to tlie stem of Halichondria 

 ventilahrum, Johnston, nat. size : a, group of vents at the apex ; 

 b b, lines indicating the disposition of the projecting spicules of 

 the surface winding round the summit, like the crown of the 

 human head ; c, form of bihamate spicules with which the 

 sarcode is charged ; d, stem of J£, ventilabrum ; e e, part of cup 

 of same. 



I^g. 10. The same, fully developed young one, nat. size, viz. l-24th of an 

 inch in diameter. 



Fig. 11. The same, magnified about 16 diameters, showing: — a, areolated 

 sarcode ; b, spicules, chiefly one-armed anchor-headed, disposed 

 in a whorl ; c, extension of anchor-headed spicules beyond the 

 peripliery of the young Tethya ; d, minute bihamates. 



N.B. The same remarks apply to this and the following figure 

 as to figs. 5 & 6. Note the disposition of the spicules in a whorl, 

 and the presence of the bihamates as distinguishing this species 

 from T. zetJandica. 



Fig. 12. The same, earlier stage : a, defined margin of ovule ; b, granular 

 plasma ; c, spicules, few in number, and aU acerate or without 

 heads, already disposed in a whorl ; d, bihamate spicules. 



Fig, 13. Tethya zetlaiidica, vertical section of fig. 2, about two-thirds of 

 nat. size : a, nucleus ; bbb, bundles of spicules radiating from 

 the centre of the nucleus to the circumference of the Tethya, 

 where they end in the papillary projections of the surface; 

 c c c, sarcode filling up the intervals between the bimdles of 

 spicules, charged with the ovules, fig. 7 ; dd d, young Tethyce 

 (magnified in figs. 5 & 6) in dilated cavities of the sarcode con- 

 nected with the excretory canal-system, fig. 14 ; e e, condensed 

 layer of sarcode forming the cortical layer of the Tethya ; ff, pa- 

 pillai-y prolongations of the same extended up upon the project- 

 ing ends of the spicule-buudles. 



N.B. All parts of this figure are of their natural size. 



Fig. 14. The same, diagram of dilated cavity of sarcode connected with 

 excretory canals, showing pendent position and forms respec- 

 tively of the young Tethyce, figs. 5 & 6 ; also openings of the 

 excretory canals : a a, fig. 5 ; hbb, fig. 6 ; cc c, openings of ex- 

 cretory canals. 



Fig. 15. The same, three young Tethyce attached to one pedicle. 



Fig. 10, The same, four figures showing the development of the one- 

 armed anchor-headed spicule, viz. : — «, simple shaft ; b, the same 

 with end inflated ; c, showing the budding of the " one arm ;" 

 d, the arm fully formed ; and e, the bud of a second arm. 

 Scale l-24th to 1-GOOOth of an inch. 



Fig. 17. The same, other spicules of the fully developed young Tethya, 

 fig. 5 : a, one-armed forked spicule analogous to the one-armed 

 anchor; c, two-armed forked spicule; b, three-armed forked 

 spicule ; d, three-armed anchor-headed spicule ; e, acerate 

 spicule. 



Of course, the ends of all these spicules, which are not repre- 

 sented, are single-pointed. 



Budleigh-Salterton, Devon. 

 25th March, 1872. 



