. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. is beset with them. They may be often most distinctly seen when their motion be- comes languid or impeded, as is the case when the water round the animal is diminished by evaporation to such a degree as not to afford scope for their full and rapid play. The cilia of the Infusoria in their arrange- ment are: either separate and independent, or combined, forming in the latter case the rota- tory or wheel-like organs of the rotiferous tribes of animalcules. In the first or simple form, which exists in the Polygastric Infuso
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. is beset with them. They may be often most distinctly seen when their motion be- comes languid or impeded, as is the case when the water round the animal is diminished by evaporation to such a degree as not to afford scope for their full and rapid play. The cilia of the Infusoria in their arrange- ment are: either separate and independent, or combined, forming in the latter case the rota- tory or wheel-like organs of the rotiferous tribes of animalcules. In the first or simple form, which exists in the Polygastric Infusoria (jig. 289), the cilia are usually set round the mouth or spread over the Fig. 289. body generally, in which case they are often disposed in regular rows. Their struc- ture has been carefully in- vestigated by Professor Ehren- berg, who states that each is furnished with a bulb at the root, to which minute muscles are attached. A slight degree of rotation communicated to the bulb causes a much more extensive motion in the rest of the organ, which in its re- Leucophrys volution describes a cone. patula. From time to time the animal sets its cilia in motion, and then, if its body be free, the cilia, acting like fins or oars, move it onwards through the water, serving in this case as organs of lo- comotion. If the body is fixed, the cilia com- municate an impulse to the surrounding water and excite a current in it. This may always be made evident by mixing with the water some colouring matter, the particles of which are hurried along by the current. Many of these particles are conveyed towards the mouth, where some are swallowed and the rest thrown back, the cilia in this case serving the animal as a means of seizing its food. In their combined form the cilia constitute the singular and well-known rotatory or wheel- like organs of the Rotiferous Infusoria. These are formed of one or more circles of cilia, placed on the fore part of the animal, as in Philodina (Jig. 290), in wh
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