. The cell; outlines of general anatomy and physiology. Cells; Anatomy; Physiology; Cells; Anatomy; Physiology. THE VITAL PROPERTIES OF THE CELL 85 also lie observed that tlie mean position through, which the cilia oscillated was different for a time in one half of the rows of cilia from that seen on the other side. III. The Contractile Vacuoles, or Vesicles, of Unicellular Organisms. Contractile vacuoles occur very frequently in Amoebag, Reticularia, Flagellata (Figs. 7, 43, 44), and Ciliata (Fig. 50 cv). In the last, where they have been most accurately ex- amined, there is generally only on
. The cell; outlines of general anatomy and physiology. Cells; Anatomy; Physiology; Cells; Anatomy; Physiology. THE VITAL PROPERTIES OF THE CELL 85 also lie observed that tlie mean position through, which the cilia oscillated was different for a time in one half of the rows of cilia from that seen on the other side. III. The Contractile Vacuoles, or Vesicles, of Unicellular Organisms. Contractile vacuoles occur very frequently in Amoebag, Reticularia, Flagellata (Figs. 7, 43, 44), and Ciliata (Fig. 50 cv). In the last, where they have been most accurately ex- amined, there is generally only one single vacuole in the whole body; occasionally two are present (Fig. 50), or rarely a few more ; they are always situated just below the sur- face of the body, under the ectoplasm. They may be easily distinguished from the other fluid vacuoles, of which larg'e numbers may be distributed throughout the body, by the fuct, that at regular intervals they discharge their con- tents to the exterior, and then gradually fill up again. Hence they tem- porarily disappear (Fig, 50 a') to reappear again in a short time (cv^). The evacuation takes place through one or more special pores, which can be observed on the surface of the infusorian immediately over the vacuole. " Each pore appears as a rule as a minute circle, the border of which is dark, but which is bright in the centre ; this brightness of the centre is due to the re- fractive power of the pellicular and alveolar layer. Sometimes each pore is connected to the vacuole by means of a fine excretory tube. In addition, it is not uncommon to find special conducting canals (1, 2, or more) regularly arranged in its neighbourhood. In. Fig. 49.—Spirostomum amhigmim. The con- tinuity of the surface which bears the peri- stomatic cilia has been interrupted by an in- cision. (After Ver worn (VI. 40), Fig. 25.) Fig. 5U. — Parammciiim caudatum semi-diagram- matic (R. Hertwig, Zoo- logie. Fig. 139) : K nu- cleus ; nh secondary nu- c
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