BRITISH SPONGIAD,E. 85 



nate spicula. The manner in which these fasciculi are 

 strengthened and supported in their places is very remark- 

 able, they are, as it were, each buttressed in its position 

 by numerous comparatively short fusiformi-acerate spicula, 

 which are based on the inner surface of the thick dermal 

 coat of the sponge, and leaning from all parts around the 

 fasciculus, their apices are concentrated around it, forming 

 a most efficient conical buttress to it in its progress through 

 the somewhat soft and yielding mass of the dermal crust 

 of the sponge. These spicula do not reach the external 

 surface of the sponge, but terminate in a cone about one 

 third or one fourth the thickness of the dermal crust 

 within its distal surface. Their dimensions are, length ^th 

 inch, greatest diameter B yth inch. 



Disposed in the surrounding sarcode there are an abun- 

 dance of very minute contort bihamate spicula. These 

 spicula are remarkably minute, an average-sized one which 

 I measured was ^rd inch long, and g^th inch diameter, 

 about the middle of the shaft. They are of a contort 

 sigmoid form, and until a section of the sponge is immersed 

 in Canada balsam they are not readily to be seen in situ. 



Dr. Johnston, in page 82 of his ' History of the British 

 Sponges,' says, " In the native species of Tethea there are 

 neither pores nor oscula, and Mr. Edward Forbes informs 

 me that in the living T. cranium, he did not observe any 

 currents of water passing into or from the body. Adouin 

 and Milne-Edwards, however, have seen their currents. 

 When a Tethea, they tell us, is placed in a basin filled with 

 sea water, and left for a considerable time perfectly still, 

 we then see distinctly all the oscula agape, and we perceive 

 also the currents which pass through them. But if the 

 animal is irritated, or withdrawn for an instant from the 

 water, the currents slacken or are altogether arrested, and 

 the oscula contracting slowly and insensibly, become at last 

 almost close." ' Hist. Nat. du Litt. de la France,' i, p. 78. 



Although I carefully examined a considerable number of 

 specimens, I could not detect either oscula or pores. The 

 interior of the sponge is very close and solid, and the inter- 

 stitial canals few in number. I cut a large specimen into 



