■'^■] THE BELL-ANIMALCULE. 87 



)f their vitality; wliile their rapid propagation is, in the 

 nain, due to their power of multiplying by division, with ex- 

 raordinary rapidity, when duly supplied with nourishment. 

 Che majority are free and provided with numerous cilia by 

 vhich they are incessantly and actively propelled through 

 ■he medium in which they live; but some attach themselves 

 ■0 stones, plants, or even the bodies of other animals. A 

 ew are parasitic, and the bladder and intestines of the Frog 

 ire usually inhabited by several species of large size. 



The Bell-animalcules are Infusoria which are fixed, 

 isually by long stalks, to water-plants, or, not unfrequently, 

 o the limbs of aquatic Crustacea. The body has the shape 

 f a wine-glass with a very long and slender stem, provided 

 ?ith a flattened disc-like cover. What answers to the rim 

 f the wine-glass is thickened, somewhat everted, and richly 

 iliated, and the edges of the disc are similarly thickened 

 nd ciliated. Between the thickened edge of the cover, or 

 eristome, and the edge of the disc, is a groove, which, at one 

 oint, deepens and passes into a wide depression, the vesti- 

 ulum. From this a narrow tube, the oesophagus, leads into 

 tie central substance of the body, and terminates abruptly 

 ierein ; and when fsecal matters are discharged, they make 

 leir way out by an aperture which is temporarily formed in 

 ne floor of this vestibule. The outermost layer of the sub- 

 ;ance of the body is denser and more transparent than the 

 3st, forming a cuticula. Immediately beneath the cuticle it 

 tolerably firm and slightly granular, and this part is dis- 

 nguished as the cortical layer; it passes into the central 

 ibstance, which is still softer and more fluid. 



In the undisturbed condition of the BeU-animalcule, the 

 ,em is completely straightened out ; the peristome is everted, 

 id the edges of the disc separated from the peristome ; the 

 jstibule gaping widely and the cilia working vigorously, 

 ut the least shock causes the disc to be retracted, and the 



