VORTICELLA. 



[ 684 ] 



WATER. 



Length of 



VORTICELLA, Linn.— A genus of In- 

 fusoria, of the family VorticelUna. 



Char. Body campanulate, with an ante- 

 rior ring of ciha, stalked; stalk simple, spi- 

 rally contractile. 



These interesting Infusoria are very com- 

 monly met with in decomposing vegetable 

 infusions, as of hay, portions of dead 

 flowers, &c. Their curious metamorphoses 

 and modes of reproduction are noticed under 

 Infusoria. 



Ehrenberg describes nine species. 



V. nebultfera (PI. 25. fig. 21). Body 

 conico-campanulate, colourless ; anterior 

 margin dilated; body without rings when 

 contracted. Length of body without the 

 stalk 1-576 to 1-288". 



V. microstoma (PI. 25. fig. 26, body with 

 gemmse). Body ovate, narrowed at the 

 ends, greenish white; anterior margin not 

 dilated, nor body ringed when contracted. 

 Length of body 1-2000 to 1-250". 



V. convallaria. Body ovato-conical, 

 whitish hyaline, annulate; expanded ante- 

 rior margin slightly prominent 

 body 1-430 to l-240''. 



Dujardin unites the genera Carchesium 

 and Zoothamnium to his genus Vorticella, 



BiBL. Ehrenberg, Jw/m5. 269 ; Dujardin, 

 Infus. 546 ; Stein, Infus., passim. 



VORTICELLINA.— A family of Infu- 

 soria. 



Char. Isolated and free, or fixed and 

 aggregate; alimentary canal with two ori- 

 fices, separate, but in the same groove ; 

 carapace none. 



The characters are very vague, and the 

 family an unnatural one. The genera 

 Stentor, Trichodina and Urocentrum have 

 little affinity with the others. In the true 

 genera, the bodies are stalked, the stalk 

 usually branched, and the cilia form a ring 

 at the anterior end of the body. 



Genera : 



Stalk absent. 

 Tail none. 



Body ciliated 1 . Stentor. 



Body smooth, cilia anterior. ... 2. Trichodina. 

 Tail present 3. Urocentrum. 



Stalk present. 



Bodies all uniform. 

 Stalk spirally flexible. 



Stalk simple 4. Vorticella. 



Stalk branched 5. Carchesium. 



Stalk inflexible 6. Epistylis. 



Bodies of two shapes. 



Stalk inflexible 7- Opercularia. 



Stalk spirally flexible S. Zoothamnium. 



BiBL. Ehrenberg, Infusoria, 259. 



W. 



WASP.— See Vespa. 



WATER.— Under this head we might 

 form a kind of index referring to a large 

 proportion of the articles of which this vo- 

 lume is composed, since water, existing under 

 different circumstances, forms one of the 

 most fertile sources of microscopic objects ; 

 but as our space and plan do not admit 

 of such an enumeration, we must be content 

 to dwell shortly upon two of the most im- 

 portant questions in which the microscope 

 is applied to the examination of the contents 

 of water. 



Ordinary examination of water. — Here it 

 appears merely necessary to point out that 

 the mode of examining the contents of sam- 

 ples of water, for the purpose of ascertaining 

 the extent to which organic beings are con- 

 tained in them, should be very different from 

 that pursued by the microscopist who is 

 engaged in collecting specimens. We make 

 this remark in consequence of the gross mis- 

 representations which are sometimes made 

 respecting the " animalcules " in water, 

 carried to their most absurd extreme in the 

 so-called "drop" of water shown by oxy- 

 hydrogen microscopes, where we often see 

 the field covered with larvae of dragon-flies, 

 of beetles, of gnats, &c., Entomostraca and 

 worms of different kinds, not only per- 

 ceptible without a microscope, but in the case 

 of the larvae, perhaps really more than an 

 inch long. Less violent exaggerations occur 

 when water which ajjpears cloudy is selected, 

 allowed to stand for some time, and the 

 sediment examined. Very false results must 

 also be obtained when water is exposed to 

 the air for any length of time before exami- 

 nation, since Infusoria and microscopic Algae 

 always appear in a short time, even in di- 

 stilled water, when exposed to the atmo- 

 sphere ; and a rain-water butt will generally 

 be found a very fertile source of microscopic 

 objects. We regard the presence of most 

 of those organisms which do not suffi- 

 ciently affect the water to render its impu- 

 rity discernible by the naked eye, as a mat- 

 ter of little consequence. Large quantities 

 of Entomostraca, certain Rotatoria and In- 

 fusoria, and Oscillatoriaceous Algae, generally 

 very perceptibly clouding or colouring the 

 water, of course indicate the presence of 

 much decomposing organic matter in the 

 water, which, however, reveals itself very 

 clearly in a short time, when the water is 

 kept, by a foetid odour. The presence of 



