CYCLOUM. 365 



uniformity and quickness which is admirable, and very 

 pleasing to the beholder. When the egg is at rest, their 

 velocity is not diminished, excepting at the will, so to 

 speak, of the ovum, for it may be seen to become slower 

 and less constant, to cease entirely for a moment, and again 

 be renewed with its former force. The egg, at rest, will at 

 once start from its place, and swim about hither and thither, 

 as it were endowed with volition, turning on its axis fre- 

 quently, moving sometimes on one side, sometimes on the 

 edge, when the cilia become invisible. By their motion 

 they drive a current of water over the surface." 



3. ALCYONIDIUM PAHASITICUM, Dr. Fleming. 



Hab. On the stalks of Sertulariada. 



This is like a blackish-brown earthy coating on several 

 of the corallines. The doubts respecting its nature have 

 been dispelled by the researches of Mr. Hassall, Yan Bene- 

 den, and Professor Reid. An interesting account of it by 

 Professor Eeid may be found in Dr. Johnston's work, page 

 362. 



Genus XXI. CYCLOUM, Hassall. 

 Gen. Char. Polypidom fleshy, encrusting, covered with nu- 

 merous imperforate papillae. Hassall. 



