An Urchin at Dinner. 235 



messengers, with a head like a microscopic sea- 

 anemone, come cautiously peering up through the 

 sandy funnel, and stretching and stretching itself out 

 for the exploration of the surface sand, and to all 

 appearance selecting tit-bits from a larder which to 

 our eyes seems to be all impartially gritty. The 

 mouth of the animal is a calcareous aperture on 

 the under side without movable lips or jaws, but 

 irregularly surrounded by processes which Forbes 

 calls "short tentacula, with discs surrounded by 

 clavate filaments." By patient attention Mr. Robert- 

 son has several times Sreen these descend and grasp 

 the sand, or other material dropped from the anterior 

 groove of the test, and convey it to the mouth. The 

 extensile hunting filaments above described appa- 

 rently convey their prey to this groove, and the small 

 spines of the groove then pass it on. The funnel in 

 the sand is kept open by a glutinous secretion exuded 

 from the body of the animal, and by a set of extensile 

 filaments which form a sort 'of palisading round it. 

 Mr. Robertson carried out a series of careful experi- 

 ments to determine the source of the secretion just 

 mentioned. This source appears to be situated at 

 the base of the spines, but it has not yet been 

 definitely ascertained. Moreover, the great volume 

 of this slime which the animal is able to discharge is 

 not yet accounted for, although the quantity of it 

 explains, what would be otherwise surprising, that a 

 creature carrying a close armature of small spines, 

 and with the habit of burying itself in the sticky sea- 

 sand, is yet able to rise from it as bright and unsullied 

 as a Venus anadyomene. 



