160 A MAEVELLOUS STEUCTUEE. 



the observer and the animal (not directly but ob- 

 liquely, so as to make the angle of reflection more or 

 less acute), the reflections will take yellow, orange, 

 scarlet and crimson hues. 



As it crawls, the Aphrodite usually elevates the 

 tail, which is so folded together as to form a deep 

 groove beneath. By watching this we see now and 

 then ejected a stream of water, with considerable 

 force. I found that the jet occurred once in twenty 

 five seconds, with punctual regularity. This is a 

 respiratory act ; the grooved orifice through which 

 the jet is poured is not the termination of the intes- 

 tine, as we may at first suppose, but the exit of a 

 capacious chamber which is external to the body, 

 though concealed. 



A very marvellous and quite unparallelled struc- 

 ture here comes into view. If we take a Sea-mouse 

 into our hand, we see the whole breadth of the back 

 occupied by a woolly substance, closely resembling felt, 

 and formed by the interlacing of fine hairs. If we in- 

 sert a pen-knife into the tail-groove and slit up this felt- 

 like cover, we expose an ample cavity running the whole 

 length of the animal, the floor of which is the true skin 

 of the back, on which are set two rows of large over- 

 lapping plates, or membranous scales {elytra). 



The dense tissue of interwoven hair resembling felt 

 acts as a filter for the water to be respired, straining 

 off the earthy particles held in it, which thus accu- 

 mulate in its substance, and impart that peculiar dirty 

 appearance which it possesses. The scales, according 

 to Dr. Williams,* are periodically elevated and de- 

 • Report on the British Annellida, 200. 



