STRUCTURAL DIFFERENTIATIONS 153 



and others, to conspicuous fibers in Diplodinium ecaiidatnm and 

 Euphtes patella (see p. 112). In the latter organism Yocom (1918) 

 and Taylor (1920) found fibers running from the posterior anal cirri 

 and from the adoral zone of membranelles to a common anteriorly 

 placed structure termed the motorium, which they regard, with 

 wSharp (1914) as a center of the neuromotor system (see p. 109). 

 The ventral and frontal cirri, however, are not connected by similar 

 fibrils with this motorium, but possess bundles of fibrils, described 

 earlier by Prowazek in Euphtes harpa, and by Griffin in E. Worcester i, 

 which may run in any direction until lost in the endoplasm (Fig. 79, 

 p. 151). The inference is that these cirri are independent of the 

 coordinated s\'stem of fibrils which regulate the adoral zone and the 

 anal cirri, and that their movements, which are always irregular, 

 are not aft'ected by cutting the coordinating fibrils of the motor 

 system (Fig. 57, p. 110, also see p. 112). 



(c) Other Organoids Adapted for Food-getting.— Mention may 

 be made here of a few special types of cortical differentiation apart 

 from the cell mouths, which Infusoria use for purposes of food- 

 getting. The most striking of these are the tentacles of Actinoholus 

 radians, the "tongue" or "seizing organ" of Vidlnhnn nasutam and 

 the tentacles of the Suctoria. 



Contractility due to myonemes is a widely-distributed phe- 

 nomenon in ciliated Protozoa and in most cases in\-olves the 

 activity of the entire organism (see p. 105). When it is limited 

 to restricted portions of the body, such as the peristomial com- 

 plex of Diplodinium ecavdatum, or the "vestibule" of Vorticellid?e, 

 it acquires a special interest. Even more remarkable than these, 

 however, is the power, possessed by Lacrymaria olor, of projecting 

 its mouth-bearing extremity any distance up to three times the 

 length of the flask-shaped body, or until the rubber-like neck is 

 reduced to a mere fibril. The "head" thus projected dashes here 

 and there with amazing rapidity, the body meantime remaining 

 quiet and unmoved, until finally the head and neck are withdrawn 

 and the cell swims ott' with no visible trace of contractile structures 

 (Fig. 76, p. 14S). Xo special myonemes have been described in 

 this form and the projection and retraction of the "head" must 

 be due to the elasticity of the cortex of the "neck" region, com- 

 bined with activity of the oral circlet of cilia while the body cilia 

 are at rest. 



Another remarkable and special phenomenon, seen apparently 

 by few observers, is the method of food-getting by Actinohclus 

 radians. This organism, when at rest, protrudes a forest of radiating 

 tentacles which stand out like axopodia, sometimes stretching a dis- 

 tance equal to several times the body diameter. The ends of these 

 tentacles carry trichocysts (Entz, Calkins, Moody) which upon pene- 

 trating an indi^'idual Ilalteria (jrandineUa, completely paralyze it. 



