68 EVENINGS AT THE MICROSCOPE. 



tissue, which may be presumed not only to line, but also 

 to cover the strong cell ; just as the strong envelope and 

 spines of a Sea-urchin are covered with a thin film of living 



The functions and use of these singular processes are as 

 obscure as their connexions with the animal. Yet that 

 they play some important part we may almost certainly 

 infer, from the general prevalence of similar or analogous 

 appendages among the various forms of this class. The 

 globular pearls which you lately saw on the Sea-mat are 

 but another form of bird's head; and the falling-door 

 answers to the opening and shutting mandible. The 

 forms, indeed, of these organs are very diverse, and some- 

 times they are greatly disguised. But what about their 

 function ? More than one observer has noticed the 

 seizure of small roving animals by these pincer-like beaks ; 

 and hence the conclusion is pretty general, that they are 

 in some way connected with the procuring of food. But it 

 seems to have been forgotten, not only that these organs 

 have no power of passing the prey thus seized to the 

 mouth, but also that this latter is situated at the bottom 

 of a funnel of ciliated tentacles, and is calculated to re- 

 ceive only such minute prey as is drawn within the ciliary 

 vortex. I have ventured to suggest a new explanation. 

 The seizure of a passing animal, and the holding of it in a 

 tenacious grasp until it dies, may be a means of attracting 

 the proper prey to the vicinity of the mouth. The pre- 

 sence of decomposing animal substance in water invariably 

 attracts crowds of infusory animalcules, which then breed 

 with amazing rapidity, so as to form a cloud of living 

 atoms around the decaying body, quite visible in the 

 aggregate to the unassisted eye ; and these remain in the 

 vicinity, playing round and round until the organic matter 

 is quite consumed. Now a tiny worm or other animal 

 «aught by the bird's head of a Polyzoon,* and tightly held, 

 * From the Greek iro\.is (polns), many, andfuou (animal). A name 



