i86 



POLYZOA. 



are called Avicularia* 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 some- 

 times equally active. 

 If we take a Poly- 

 zoon of this descrip- 

 tion, 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 crea- 

 tures 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 Aviculariae ; and hence 

 the conclusion is pretty general that they are in some way con- 

 nected with the procuration of food ; seeing, however, that these 

 organs have no power of passing the prey thus seized to the 

 mouth of the Polyzoon, and, also, that this latter is situated at 

 the bottom of a funnel of ciliated tentacula, and calculated only 

 to receive such minute prey as is drawn within the ciliary vortex, 

 it is difficult to see how this can be effected. Mr. Gosse has 

 suggested a very ingenious explanation. The habit of seizing a 

 passing animal, and holding it with a tenacious grasp until it dies, 

 may be a means of attracting a supply of food into the vicinity. 

 The presence of decomposing animal matter in water invariably 

 congregates crowds of Infusorial animalcules, which breed with 



FlG. 185. BOWERBANKIA. 



Avicula, a little bird. 



