198 ACTINOZOA. 



familiarly known as Sea-anemones. A typical 

 Sea-anemone, when contracted, may be compared 

 to a more or less depressed cone, rounded above, 

 with a gently spreading base; when expanded, 

 to a column, for the most part cylindrical, but 

 widening somewhat towards its extremities {fig. 

 34, a). The base is scarcely broader than the 

 column in some species ; in Adamsia, on the 

 other hand, it is ovate in form, sending forth two 

 lateral lobes, which extend so far as to surround 

 the aperture of the univalve shell on which this 

 curious animal-flower is found, the lobes at length 

 uniting by a zigzag suture along the outer lip of 

 the shell. As in the case of Hydractinia, the 

 shells which Adarasia selects appear always to be 

 tenanted by a species of Hermit-crab. 



The column may have its surface marked by a 

 variety of epidermic growths, or pierced by sundry 

 apertures. In Actinoloba its summit rises into a 

 conspicuous ridge, separated from the outer series 

 of tentacles by a deep depression or furrow. Oc- 

 casionally, as in the same genus, the margin of 

 the disc is waved or thrown into sinuous folds, so 

 that the arrangement of the tentacles appears 

 thereby somewhat confused. The peristomial space 

 may also vary in size, and relative depression or 

 elevation. The lips of the mouth undergo their 

 own modifications, and, in some genera, a groove 

 with mouth-tubercles occurs at but one of the oral 

 angles. In Actinopsis these tubercles are produced 

 upwards to form a pair of long, rigid, semi- 

 cylinders, the lateral margins of which again bend 

 downwards to terminate in cleft extremities. 



In the non-adherent Sea-anemones, such as 

 Hyanihus and its allies, the column is propor- 



