34 INFUSOEIA. 



last chapter. Those provided with flagelliform filaments which they 

 employ as instruments of locomotion, such as the Monadina, Crypto- 

 monadina, Pandorina, Chlamidomonas, and Volvox of Ehrenberg, are 

 now unhesitatingly admitted to belong to the vegetable kingdom ; so 

 that the ciliated forms alone are left to the zoologist, and offer them- 

 selves for our study upon the present occasion. 



(66.) The movements of the CILIATED INFUSORIA, when seen under 

 the microscope, are frequently exceedingly vivacious ; they swim about 

 with great activity, avoiding each other as they pass in their rapid dance, 

 and evidently directing their motions with wonderful precision and 

 accuracy. Our first inquiry therefore must be concerning the organs of 

 locomotion which they possess. These are of various kinds, and are 

 arranged differently in different species. Some are provided with styll, 

 or articulated, stiff, bristle-like organs, which are moveable, and perform 

 in some measure the office of feet, and with uncini, or little hooks, 

 serving for attachment to foreign bodies ; these are seen in Euplotes 

 Charon (fig. 15, 4). 



(67.) But the most important locomotive agents are the cilia*, with 

 which these Infusoria are invariably furnished. On attentive examina- 

 tion, their body will be found to be entirely covered with minute vibrating 

 hairs, or at least furnished with such appendages on some part of its 

 surface (fig. 15, 1, 2, 3). The existence of these cilia is readily detected 

 by a practised eye, even when using glasses of no very great magnify- 

 ing power, by the peculiar tremulous movement which they excite in 

 the surrounding fluid, somewhat resembling the oscillations of the 

 atmosphere in the neighbourhood of a heated surface ; but on applying 

 higher magnifiers, especially if the animalcule is in a languid state, the 

 motion is seen to be produced by the action of the delicate filaments of 

 which we are speaking. Although extremely difficult accurately to 

 define the motion of the individual cilia, it is obvious that the combina- 

 tion of their movements gives rise to currents in the water, serving a 

 variety of purposes in the economy of these minute beings. 



(68.) The cilia, as has been already observed, are sometimes dis- 

 persed over the whole body, either arranged in parallel rows or scat- 

 tered irregularly ; they are, however, most frequently only met with in 

 the neighbourhood of the mouth, in which position they are always 

 most evident: here they produce, by their vibration, currents in the 

 surrounding fluid, which converge to the oral aperture, and bring to the 

 mouth smaller animalcules, or particles of vegetable matter, which may 

 be floating in the neighbourhood, thus ensuring an abundant supply of 

 food, which, without such assistance, it would be almost impossible for 

 these little creatures to obtain. 



(69.) With the locomotive organs of these minute beings must like- 

 wise be classed the delicate and highly irritable stems of the Vorticellcv 

 * C ilium, an eyelash. 



