270 ANATOMY AND PHYSIOLOGY 



FIG. 



of them in the same slide, and they are all angu- 

 lated to the same extent. It is probably an inter- 

 nal defensive spiculum. 



244, 245, 246. TUBERCULATED FUSIFORMI - CLYINDRI- 

 CAL. The beautiful spiculum represented by Fig. 



244, X 660 linear, is siliceous. It has been re- 

 peatedly found in the matter obtained by washing 

 the roots of Oculina rosea and other corals from 

 the South Sea, by my friends Messrs. Matthew 

 Marshall, Legg and Ingall, but the sponge, whence 

 it is most probably derived, has never yet been 

 determined. It is remarkable as being the only 

 well-defined and perfect siliceous spiculum that 

 has yet been observed to possess the short stout 

 tubercles that are so characteristic of its structure. 

 Fragments of two other spicula, possessing similar 

 characters, have been observed by me, and are re- 

 presented by Figs. 245 and 246. In the specimen 

 represented by Fig. 246, X 260 linear, the tuber- 

 cles are less in number, but are considerably more 

 produced, and their terminations are more abruptly 

 truncated. In the spiculum represented by Fig. 



245, X 260 linear, they are still more widely dis- 

 tributed, are shorter and more inclined to be coni- 

 cal, so that there is little doubt that they have be- 

 longed to three distinct species of sponge. But in 

 all three of them there is one peculiarity, that of 

 the manner of the disposition of the tubercles on the 

 shafts of the spicula, where we observe them to be 

 disposed in more or less regular longitudinal lines, 

 and that the tubercles forming each line alternate 

 with those of the line next to them, so that they 

 assume the appearance of a spiral arrangement. 

 The close alliance in the structure of these spicula 

 would seem to indicate the existence of a peculiar 

 tribe of sponges, with which we are at present en- 

 tirely unacquainted. 



