" 384 EVENINGS AT THE MICROSCOPE. 



The greater portion of the shell is not smooth, has no 

 such porcelain-like polish as the Natica usually has, 

 but is clothed with a sort of downy nap, a coarse 

 sponginess of a greyish hue, splashed with yellowish 

 and pink tints. The shell is invested with Hydr ac- 

 tinia. 



"We restore the strange partnership — shell, fleece, 

 and crab — to the glass of sea-water ; where we soon see 

 the whole tumbling about the bottom in uncouth 

 agility. Assist your eye with this pocket-lens, and 

 look again. The shaggy nap upon the shell now bristles 

 with tall slender polypes, crowded and erect, like ears 

 of corn in a field. 



No high power of magnification is necessary to 

 furnish us with considerable entertainment from this 

 populous colony. The polypes stand individually 

 nearly half an inch in height; each consists of a 

 straight slender column, surmounted by eight straight 

 rod-like tentacles, four of which stand erect, slightly 

 diverging, and the other four, alternating with these 

 at their origin, extend horizontally like the arms of a 

 turnstile. 



The rough jolting of the crab over the stones the 

 expanded polypes bear with equanimity ; they are used 

 to it; and though their tentacles wave and stream 

 hither and thither, they are not retracted on this 

 account. But just touch with the point of the pencil 

 in your hand any part of the shaggy fleece, and in- 

 stantly the whole colony retire together, as if by a 

 common impulse, apparently shrinking into the sub- 

 stance of the shell. Yet they soon re-appear, one after 

 another quickly protruding its closed tentacles, which 

 are presently expanded as before. 



