PENNATULID.E. 65 



one against the space between the two on the other side. 

 They are beautifully transparent^ and have the power of 

 contracting, so as to lie up closely imbricated upon each 

 other, pressing the stalk ; but they can also expand and 

 lie out, so as to leave open spaces between. Mr. Harvey 

 says, "The polypes are objects of great beauty, and their 

 form may be very well seen after death ; for though 

 capable of retractation within the cell, the tentacula have 

 no contractile power, and may be made to expand in 

 their full extension by merely pressing upon the cell. 

 The polype thus displayed is an eight-rayed star, the rays 

 curved backwards, channeled and elegantly pectinated along 

 each margin. In the centre is the mouth, with prominent 

 lips.^' 



The same question occurs as to the habits of this Asteroid 

 as arose respecting those of Pennatula. But one curious 

 motion has been observed in the former when captive, which 

 does not take place in the latter : it is that of the animal 

 twisting itself spirally round its central axis, and afterwards 

 relaxing again into a straight line. The bone running 

 through the central axis is very slender, — said to be not a 

 thousandth part of its length in diameter. '' Each organ,'' 

 remarks Dalyell, " of this remarkable object has a distinct 



