TNrrSOEIAL ANIMALCULES. 13 



individual existence, and is traneformcd into a simple cnpsiilc. Thi3 

 organization is met with only in tho rolygastrica and more particu- 

 larly in tlie genera Vohox, Eudorina, Pandorina, and Gonium. 



"Where a lorica exists it may be made up of two or more separable 

 segments, called valves, when of two, it is said to be bivalved ; when 

 of more multivalved. The valvular form of lorica is chiefly met with 

 in the gi-eat family Bacillaria, and it is such lorica that more particu- 

 larly present a seidptiu-cd surface, and have been employed by 

 microscopists as tests (sec family BaciUaria, Part III). Some lorica 

 are also furnished with appendages, or processes, projecting in the 

 foiTu of si)ines or knobs from theu' surface. 



As, in verj' minute genera, it is often difficult to ascertain, by mere 

 inspection, whether they arc enclosed within a lorica or not, it will 

 not be deemed uninteresting to point out the manner in which this 

 may be determined. Having obtained some specimens of the Infu- 

 soria, we will suppose of the family Cryptomonas {fgs. 21 to 33), 

 place a di'op of water containing them in an aquatic live-box, com- 

 pressor, or crush-box, mixing a httle colouring matter with the water, 

 according to the directions given in the section " On feeding Animal- 

 cules with coloured Materials,^'' when, if loricated, a clear transparent 

 ring will be observed, encircling the animalcules, and keeping them 

 separate from the fluid in which they are immersed. Should this 

 test, however, bo deemed imsatisfactory, press down the cover of the 

 aquatic live-box, so as to crush the specimens, when the colom^ed 

 fluid will enter and suiTound their bodies, and by a proper manage- 

 ment of the illumination of the microscope, the broken edges of the 

 lorica wiU be \'isible, as seen mfig. 33, which is a representation of 

 the Trachclomonas volvocina, similarly circumstanced. 



Until recently, many of the genera of tho smaller kinds of ani- 

 malcules were supposed to be devoid of any external organs whatever; 

 but the feeding on coloured substances, and the introduction of 

 achromatic glasses, have proved the incorrectness of this conclusion, 

 even as respects the Monads. The simplest external member, observ- 

 able in the Infusoria, is a single, delicate, hair-like filament, differing 

 much in length, situate near tho oral orifice or mouth, whence it has 

 been designated the 2>i'ohoscis. When tliis member is of an imiforni 



