. The Protozoa. Protozoa. THE INFUSORIA 179 disk where their course is radial. The largest and most important of all of the myonemes are those forming the fourth set. These are longitudinal muscle-fibres of considerable thickness running from the centre of the disk radially toward the periphery, then continuing down the sides of the bell as far as the ciliary girdle ( Wimperring), where they leave the wall of the body and come together to form the thick muscle-strand of the stalk. The latter highly contractile organ consists of a wall and of the central, contractile strands which are bathed wi
. The Protozoa. Protozoa. THE INFUSORIA 179 disk where their course is radial. The largest and most important of all of the myonemes are those forming the fourth set. These are longitudinal muscle-fibres of considerable thickness running from the centre of the disk radially toward the periphery, then continuing down the sides of the bell as far as the ciliary girdle ( Wimperring), where they leave the wall of the body and come together to form the thick muscle-strand of the stalk. The latter highly contractile organ consists of a wall and of the central, contractile strands which are bathed with a fluid contained within the walls of the stalk. The wall itself, according to Entz, but contrary to Biitscbli, is a continuation of the living wall of the bell, in which membrane and underlying mus-. A Fig. 96. — Zoothamnium arbuscula Ehr. [ENTZ.] A. Lower portion of main trunk. B. One of the branches of the main trunk, a, axoneme; p, spasmoneme ; s, spironeme. cular structures can be distinguished, as in the main portion of the body. Biitschli, on a less substantial basis, described the stalk as a secretion similar to the stalks of the Mastigophora and Sarcodina, and chitinous in composition. The main strand within the stalk is formed by the collection of the strands of the inner longitudinal myonemes, and is covered by a delicate sheath which separates it from the fluid or gelatinous matter surrounding it. Biitschli regards this sheath as a continuous coat from the alveolar layer of the bell. The strand has three threads which Entz calls spasmoneme, spironeme, and axoneme (Fig. 96). The fibres of the first run to the base of the stalk. The other two are closely connected, and both are made up of microsomes, which Entz described as nucleus-like grznu\es(karyophans) surrounded by an ovoid matrix (cytophan). These granules, so conspicuous in the stalks of Vorticella, evidently correspond to the Elementar-Granida (Greeff, '71) or cyto-microsomes. Entz figured them as arrang
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