276 ANATOMY AND PHYSIOLOGY 



FIG. 



290. Verticillately spinecl internal defensive spicula from a 



keratose sponge, from the West Indies. Congre- 

 gated in fasciculi. X 175 linear. Pages 3 land 

 125. 



291 . A small portion of Hymeniacidon Cliftoni, Bowerbank, 



MS., exhibiting the membranous tissues of the 

 sponge enveloping the fibres of a Fucus; the defen- 

 sive spicula over the fibre being erect, whilst those 

 on the adjoining membrane are recumbent. X 1 08 

 linear : a, one of the attenuate-cylindrical internal 

 defensive spicula. X 260 linear; b, a small portion 

 of the surface of the Fucus showing its cellular 

 structure. X 400 linear. Pages 31 and 125. 



292. A portion of the reticulated specimen of the sponge 



with the radiating fasciculi of spinulo-quaternate 

 internal defensive spicula in situ. X 108 linear. 

 See also Pig. 76, Plate III. Pages 23, 33, and 122. 



293. A portion of the reticulated skeleton of Hymedesmia 



Joknsoni, Bowerbank, MS., from Madeira, the fibres 

 armed with trenchant contort bihamate spicula. 

 X 50 linear. One of the trenchant contort biha- 

 mate spicula, showing the cylindrical form at the 

 curves of the hook and the middle of the shaft, and 

 the trenchant edges of the rest of the inner sur- 

 faces of the spiculum, X 400 linear, is represented 

 by Pig. 112, Plate V. Pages 35 and 127. 



294. A portion of the skeleton of Hyalonema mirabilis, 



Gray, showing the mode of disposition of the mul- 

 tihamate birotulate and spiculated cruciform spicula 

 in the body of the sponge. In the collection at 

 the British Museum. X 50 linear. One of the 

 multihamate birotulate, X 175 linear, is repre- 

 sented by Fig. 60, Plate III, and Fig. 294, Plate 

 XVIII. Pages 37 and 127. 



295. Represents a spiculated cruciform spiculum from 



the same sponge, to show the relative proportions 

 of the two forms of defensive spicula. X 175 

 linear. Pages 37 and 127. 



