A FLOATING ACTINEA. 



121 



the sea, even far from land. One species of 

 these is about an inch long, of a yellowish - 

 brown colour, and having a mouth surrounded 

 by two circles of tentacula, the outer one long 

 and the inner short. When swimming — its 

 usual habit — it assumes a pyriform, or rather 

 elongated bell-shape, and, directing its hinder 

 extremity forwards, it propels itself througli 

 the water by alternate contractions and expan- 

 sions of its body, exactly in the manner of a 

 Medusa. But, when by the shore, or placed 

 in a vessel filled with sea- water, it changes 

 shape, dilates its hinder extremity into a suc- 

 torial disk, by which it fixes itself to stones, 

 weeds, or the sides of the glass, and assumes 

 its normal form as an Actinea. 



The true Medusae, and probably the Khizos- 

 tomoi and Cepheai, are evidently distinguished 

 by Aristotle, when he speaks of marine animals 



