32 STRUCTURE OF THE TENTACLES. 



extent to which it was clothed with coarse gTavel, and 

 for the tenacity with which it held fast its strange 

 stony garment, not dropping a fragment even after 

 several days' captivity. In general Actiuup drop 

 their gravel coats soon after they are put into a vessel 

 of clear water. 



It is for the most part a stationary species, and that 

 not only in its own selected hole in the rock-pool, but 

 even in captivity. It seldom leaves the spot in the 

 glass vessel to which it has once attached itself I 

 have had a specimen, however, take it into his head 

 to he a traveller, after several weeks' residence in one 

 spot : he walked off in a straight line to a distance of 

 four inches, performing the feat, at a pretty uniform 

 rate, in about eight hours, or half-an-inch per hour. 



In order to examine the structure of the tentacles 

 I oiit off with a fine pair of scissors the tips of one or 

 two, and submitted them to the microscope upon the 

 compressorium. As soon as the pressure began to 

 flatten them, it became apparent that the tentacle was 

 composed of rather thick gelatinous walls surrounding 

 a tubular centre. The latter was filled with a vast mul- 

 titude of very minute granules of a rich sienna-brown 

 hue, and almost quite globular in form ; all being 

 quite alike in shape, colour, and dimensions. These 

 escaped by thousands, on the increase of the pressure, 

 from the tip of the tentacle, where there was evidently 

 a natural orifice forced open by the pressure, but or- 

 dinarily, as I suppose, kept firmly closed by muscular 

 action. The gelatinous walls of the tentacle con- 

 tained, imbedded in their substance, a goodly number, 

 (not so immense as in some other species) of those 



