POLYPI. 161 



3. Polypi/era. 



THE next step in the organic series introduces 

 us to the extensive family of Polypi/era. The 

 transition from the structure of the sponge to that 

 of the polypus may be thus conceived. Suppose 

 the absorbing orifices of the former to be enlarged, 

 and their number to be at the same time re- 

 duced : arid let these orifices be drawn out into 

 tubes, and provided with vibratory cilia; in 

 addition to which, let there be placed around 

 their margin a circular row of larger filaments, 

 extremely flexible, and capable of twining 

 round any object that comes within their reach, 

 and of conveying it to the central orifice, 

 which performs the office of a mouth. Each 

 tube, thus furnished with a circle of radiating 

 filaments, or tentacula, as they are called, is 

 denominated a Polype* The animal structure 

 thus composed has received the name of JLo- 

 bularia (Fig. 56), and is the genus among this 

 tribe that approaches the nearest in its cha- 

 racter to the sponge, which it resembles in the 



* For the sake of greater distinctness I shall employ the term 

 polype to denote the single tube with its tentacula ; and shall 

 designate by the Latin term polypus the entire animal mass com- 

 posed of an aggregation of these polypes. Polypifera, the name 

 of the order, expresses animals bearing polypes. 

 VOL. I. M 



