-INFUSORIA. 49 
ture of the mouth, which is continued into a short funnel-shaped 
gullet. The gullet, however, is not continued into any distinct 
stomach, but opens directly into thesoft semi-fluid sarcode which 
constitutes the central abdominal cavity. The particles of food 
on passing through the gullet ‘are directly received into the 
central mass of diffluent sarcode, where they undergo a kind of 
slow circulation or rotation. As in the case of the Amw@ba, 
each particle of food generally carries with it a little water, so 
that the appearance is produced of a number of little clear 
spaces in the central sarcode. These are now called vacuoles, 
or food-vacuoles ; but they were originally described by Ehren- 
berg, the famous Prussian microscopist, as so many distinct 
stomachs, in consequence of which he named the /z/fusoria the 
Fig. 13.—Ciliated Infusoria. A. Paramecium, showing the nucleus (7) and two 
contractile vesicles (v). B Paramecium bursaria (after Stein) dividing trans- 
versely : 2 Nucleus; %’ nucleolus; w Contractile vesicle. C Paramecium 
aurelia {after Ehrenberg), dividing longitudinally. 
Polygastrica (Gr. polus, many; and gaster, stomach). The 
vibrating cilia which clothe the surface of Paramecium serve 
partly to drive the animal rapidly through the water, and partly 
to set up currents by means of which food is conveyed to the 
mouth. All the nutrient particles obtained in this way undergo 
the circulation in the central sarcode above spoken of, where 
they are partially or completely digested. The indigestible por- 
tions of the food appear to be got rid of by a second aperture 
(anus) placed near the mouth. The only other organs pos- 
sessed by Paramecium are the so-called nucleus and nucleolus, 
D 
