HABITS OF THE POLYZOA. 409 



in a vessel of sea- water, however, it is by no means 

 difficult to detect, with a magnifying glass of very 

 ordinary power, that every fibre of these moss-like 

 patches is alive ; nay, more, that it is an animal of 

 most elaborate structure, polyp-like in form, and, 

 like the humbler polyps, living in a cell, sometimes 

 of horn, transparent as thin glass, sometimes with 

 fleshy, or with earth-encrusted walls. A little further 

 inspection shows that the polyp-shaped occupants 

 of these cells are full of life and vivacious activity, 

 readily, when undisturbed, protruding from the ori- 

 fices of their abodes their numerous delicate and 

 flexile arms in search of food : 



"As florets, by the frosty air of night 

 Bent down and closed, when day has gilt their leaves, 

 Rise all unfolded on their straighten'd stems * ;" 



but which on the slightest alarm are instantly re- 

 tracted and packed up securely in their little citadel. 

 The gentlest touch, even the modifications of the in- 

 tensity of light, are sufficient to produce the retire- 

 ment of these timid creatures, which thus manifestly 

 exhibit both an apprehension of danger and a feeling 

 of safety. 



The cells, though commonly still, have a free 

 power of motion ; and when one is disturbed, it bends 

 quickly to and fro, so as to strike one or two more ; 

 these again strike upon others, and thus, for a few 

 seconds, all are in action, banging themselves about 



* " Quale i fioretti, dal notturno gielo 



Chinati e chiusi, poi che '1 sol gl' imbianca 

 Li drizzan tutte aperte in loro stelo." 



