Text-book of comparative anatomy . theseizing and sucking in of food, and for the formation of currents which PROTOZOA 17 bring it within reach. There are no special points of the body forthe taking in of food in the Monera, Sarcodina, Gregarina, Suctoria, andthose Flagellata which feed after the manner of plants. In otherFlagellata and in the Infusoria, there is at one special part of the body(in the Flagellata at the base of the chief flagellum) a depression ofthe ectoplasm (mouth and oesophagus), through which solid food ispassed into the endoplasm. In the In-fusoria there are, closely conn
Text-book of comparative anatomy . theseizing and sucking in of food, and for the formation of currents which PROTOZOA 17 bring it within reach. There are no special points of the body forthe taking in of food in the Monera, Sarcodina, Gregarina, Suctoria, andthose Flagellata which feed after the manner of plants. In otherFlagellata and in the Infusoria, there is at one special part of the body(in the Flagellata at the base of the chief flagellum) a depression ofthe ectoplasm (mouth and oesophagus), through which solid food ispassed into the endoplasm. In the In-fusoria there are, closely connected withthe mouth, cilia specially arranged, incircles or spirals, which whirl into it theminute nutritive particles. A certain partof the body may also temporarily functionas mouth. In this case the aperture isonly visible at the moment of anal aperture or anal spot can alsobe found for the evacuation of undigestedremnants of food. I V. Adaptations for Excretion. The so-called contractilemay, with doubtful accuracy,. w FIG. 20.—Paramecium aurelia. M,Medulla ; C, cortical layer ; n, macro-nucleus ; n, micxonucleus ; en, cuticle ;ci, cilia ; t, tricnocysts ; v, food vacu-o, cell mouth or1, 2, 3, 4, Form- vaeuoles be con-sidered as adaptations for excretion, removing from the body the uselessproducts of metabolism. These vaeuolesare found in most Amaba, Heliozoa,Flagellata (excepting Cystoflagellata), and Infusoria, but are Wanting in the RhlZO- ation ofvacuole (after Ray Lankester). poda, Eadiolaria, Gregarina, and Cysto- flagellata. They vary greatly in number. Where there is only oneit generally has a fixed position. There is no sharp distinction be-tween contractile and non-contractile vaeuoles. The first are vaeuoleswithout walls, filled with liquid, which in cases where a differentiationinto ecto- and endo-plasm exists generally lie in the former. Theygradually expand and then contract more quickly, often and during contraction they mo
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