122 



PLUSTBA. 



are the Flustrce, for an example of which see 

 plate E, fig. 2. These creatures do, indeed, 

 much resemble the leaf of some plant, and so 

 closely that uneducated people can hardly be 

 made to believe their animal origin. If, how- 

 ever, the fingers are passed over the surface of 

 the flustra, and especially if they are passed from 

 the point of the leaf towards the base, a peculiar 

 rough, harsh, and stony sensation will be per- 

 ceived, and this sensation is caused by the innu- 

 merable spine-crowned cells with which the leaf 

 is covered, and, indeed, of which it is composed. 

 A close examination with the naked eye shows 

 that there is a curious structure not usually 

 met with in plants; but if an ordinary pocket- 

 lens is brought to bear on it, the entire surface 

 will be seen to be composed of little oval cells, 

 arranged in rows something like the scales of a 

 fish, or tiles on a house-top. Each cell is armed 

 with four short, sharp spines, that project from 

 the upper portion of the edge, two at each side, 

 and these spines are the cause of the peculiar 

 rough sensation that is communicated to the 

 finger. The cells are placed back to back, like 

 those of a honeycomb, so that there is no right 

 or wrong side to the flustra leaf 3 for leaf it must 

 be called, although its proper title is polypidom. 



