246 POLYZOA. 



found to consist of three portions. The lower part is 

 stiff and horny, though quite pellucid ; towards its 

 upper third, however, it becomes flexible, and at 

 length terminates in a marginal row of delicate 

 horny filaments, united by a web or membrane of 

 exquisite tenuity. Above these filaments the ciliated 

 tentacles expand, and form a sort of funnel, of which 

 the mouth is the apex or centre. Though the 

 tentacles are commonly stiff and motionless when 

 expanded, they are highly sensitive, and on the least 

 alarm are drawn within the tube, the mouth of which 

 is then closed by the beautiful mechanism above 

 described, the horny filaments that surround it 

 closing over them, as represented in the engraving. 



Many species of these marine Polyzoa are furnished 

 with numerous organs appended to the exterior of 

 the cells, which are of a most remarkable and inex- 

 plicable character. These organs are called Avicu- 

 laria* and resemble vultures' heads; not a cell is 

 without its bird's head, and all are employed in see- 

 sawing, snapping, and opening their jaws with the 

 most amusing activity. Nay, strange to say, even in 

 specimens, the animals of which are all dead, these 

 "birds' heads" are sometimes equally active. If we 

 take a Polyzoon of this description, and drop it, while 

 in full activity, into a narrow glass cell, with parallel 

 sides, filled with the purest sea-water, and here 

 examine it with the microscope, the Polype-like 

 creatures protruding their crystal stars of tentacles, 

 the birds' heads nodding to and fro their bald pates, 

 and opening and shutting their frightfully gaping 

 jaws like snapping turtles, form altogether a scene 

 quite indescribable. 



More than one observer has noticed the seizure of 

 small roving animals by the pincer-like beaks of the 

 Avicularise ; and hence the conclusion is pretty 

 general that they are in some way connected with 

 the procuration of food ; seeing, however, that these 

 organs have no power of passing the prey thus 



* Avicula, a little bird. 



