GraycUa, Osculina, and Cliuiui. 77 



No two papilhe, us before stated, presented exactly the saiiu; 

 t'orin ; but the general |)laii in all was that described. 



When exposed to the direct rays of the sun, the inhalant 

 areae all contracted, while the six vents, on the contrary, ap- 

 peared to be, if anything, more expanded by the same stinnilus, 

 — showing, also, that sponges are sensible to light. The 

 inhalant arcic also contracted on motion, while the vents 

 rt'iiiained unaltered ; so that, to observe the former in an 

 expanded state, it was necessary to subject them to as little 

 motion as possible while bringing them under microscopical 

 examination. In short, the vents were seen to continue 

 their office while that of the inhalant arcie appeared to be 

 suspended. 



I could see, with the microscope, particles issue from the 

 vents, but could never do so, one way or the other, from the 

 apertures of the inhalant arete ; nor could I see any signs of 

 an inhalant cun'cnt in the latter by the addition of finely 

 levigated solutions of both carmine and Indian ink, applied 

 separately, such as, under similar circumstances, may always 

 be seen in SpongiUa. 



Then it should be remembered that the incarcerated CUona 

 is probably nom-islicd by the remains of animal matter in the 

 substance of the oyster-shell in which it burrows, Avhile Spon- 

 yilla and the free sponges must obtain it from the surrounding 

 element : hence the inhalant area in the former may be much 

 less active than in the latter ; and hence particles of refuse 

 matter may be seen to issue from the vents in CUona while 

 the inhalant arete are closed. 



The largest holes of the vent-papillae (which only contained 

 one each) were 30-800tlis of an inch in diameter, and the 

 largest a])ertures in the inhalant areas about the 600th of an 

 inch in diameter ; in short, the former were not much less than 

 thirty times as large as the latter. 



Spiciiles. — The smooth, nearly straight, pin-like spicules 

 of CJiona northnmhrica, which are by far the largest, viz. 

 73-(3000ths or l-82nd of an inch long in the interior, chiefly 

 occupy the papilla, where, although a little less in size, they 

 exist exclusively of all others and are so numerous as to form 

 the greater part of its bulk ; the largest spinous curved fusi- 

 form spicules, pointed at each end, which chiefly occupy the 

 sarcode of the interior, are about 25-6000ths inch long ; and 

 the minute sinuous ones which accompany them 3-G(>00ths of 

 an inch. Thus we have the si)icule-formula of C. northumhrica 

 given by Mr. Hancock (/. c), saving the unimportant trifling- 

 discrepancy in measurement. 



Lastly, similar sponge-substance to that of the interior, 

 which was present in retiform patches on the exterior ot the 



