SPICULA FROM SPONGES. 291 



expando-ternate, arranged at angles at 45 to the other 

 part of the stem (Fig. 169, No. 7) ; there is also in this 

 kind a variety having spicula sharp at one end and ex- 

 panding into three branches at the other, each of which is 

 again divided. In the genus Tethea there are spicula 

 having hooks at both extremities bi-recurvo-ternate : at 

 one end they are not so large or so numerous as at the 

 other ; the stem is a little spinous. In Tethea Lyncuriitm 

 the ends of the branches of the spicula are recurved, 

 forming two, three, or four hooks, which serve to anchor 

 the crust to the soft central fleshy part ; they are termed 

 recurvo-binate, and ternate. Of the recurvo-ternate we 

 give a specimen from a species of Pachymatisma (fig. 169, 

 No. 7). 



Among the genus Grantia, Geodia, and Levant sponge, 

 are found spicula of a large size, radiating in three 

 directions triradiate. In the Levant specimen, a central 

 communicating cavity can be distinctly seen. Some 

 Smyrna sponge, and a species of Geodia, have four rays 

 quadriradiate. Some spicula in P. Johnstonia and Geodia 

 have as many as ten rays multiradiati. In some species 

 of Tethea and Geodia the spicula consist of a central sphe- 

 rical body, from which short conical spines proceed 

 stellate spicula. (Fig. 169, Nos. 4 and 5.) Spicula having 

 both extremities bent alike bicurvate have been ob- 

 tained from Trieste sponge. Some South Sea sponges 

 have spicula twice bent, and have extremities like the 

 flukes of an anchor bicurvate-anchorate ; sometimes 

 the flukes have three pointed ends. (Fig. 169, No. 6.) 

 The gemmules in fresh-water sponges are generally found 

 in the oldest portions near the base, and each one is pro- 

 tected by a framework of bundles of acerate spicula of the 

 flesh, as shown in fig. 169, No. 9 ; but in many marine 

 species, Geodia and Pachymatisma, they are principally 

 confined to the crust. In the fresh-water sponges, the 

 amount of animal matter in the gemmules is considerable ; 

 but in Pachymatisma, Geodia, and many other marine 

 species, a very small quantity only is ever to be found, the 

 substance of each gemmule being almost entirely composed 

 of minute siliceous spicula ; and if they be viewed when 

 taken fresh from the sponge, and after boiling in acid to 



