266 AN HOUK AMONG THE TORBAY SPONGES. 



endowed with the faculty of waving to and fro in 

 given directions at the will of the animal (for, strange 

 as it may sound to some of my readers, a Sponge is, 

 beyond all controversy, an animal), and in rhythm 

 or harmony with one another ; and these regular 

 wavings impart movement to the water, and cause 

 currents to flow in a given direction through the 

 canals. 



These spicula or needles, however, that make up 

 the firm portion of the Sponge, are worthy of a little 

 notice. Without them the creature would be a mere 

 drop of glaire, having neither form nor consistence. 

 And yet a heap of needles seems to have little power 

 of assuming or of keeping any definite corporate form, 

 when we remember that they have no adhesion to 

 each other, and nothing, in fact, to keep them toge- 

 ther but their mutual interlacement, and the thin 

 glaire by which they are invested. 



In order to obtain a good idea of their structure 

 and appearance, we should take one of the white 

 species, such as the flattened sac that is so commonly 

 seated on the stems of the red algse, several of which 

 we have taken at Koundham Head. 



In these the constituent substance of the spicula is 

 not flint, but lime ; but the delicacy, beauty, lustre, 

 transparency, brittleness, smoothness, and fineness of 

 the glass are the same in both cases. As we must 

 use a very high magnifying power, so we can observe 

 only a very minute portion at once ; hence the best 

 mode is to tear one of the little sacs apart, and with 



