162 BIOLOGY OF THE PROTOZOA 



they regard, with Sharp (1914), as a center of the neuromotor sys- 

 tem (see p. 129). 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 Euplotes harya, and by 

 Griffin in E. ivorcesteri, which may run in any direction until lost 

 in the endoplasm. The inference is that these cirri are independent 

 of the coordinated system of fibrils which regulate the adoral zone 

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

 irregular, are not affected by cutting the coordinating fibrils of the 

 motor system (Fig. 72, p. 130, also see p. 131). 



(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 Actinobolina 

 radians, the "tongue" or "seizing organ" of Didinium nasutum and 

 the tentacles of the Suctoria. 



Contractility due to myonemes is a widely-distributed phenome- 

 non in ciliated Protozoa and in most cases involves the activity of 

 the entire organism (see p. 124). When it is limited to restricted 

 portions of the body, such as the peristomial complex of Diplodi- 

 nium ecaudatum, or the "vestibule" of Vorticellidae, 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 unmoved, until finally the head and neck are withdrawn and the 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 off with no visible trace of contractile structures (Fig. 85, 

 p. 156). No 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, combined with 

 activity of the oral circlet of cilia while the body cilia are at rest 

 or relatively quiet. 



Another remarkable and special phenomenon, seen apparently 

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

 radian:-!. This organism, when at rest, protrudes a forest of radiat- 

 ing tentacles which stand out like axopodia, sometimes stretching 

 a distance equal to two or more times the body diameter. The 

 ends of these tentacles carry trichocysts (Entz, Calkins, Moody) 

 which upon penetrating an individual Halteria grandinella com- 

 pletely paralyze it. The tentacle, then, with prey attached, is 

 withdrawn entirely into the body, the Halteria is worked around 

 to the mouth and swallowed (Fig. 91). Actinobolina vorax (Wen- 

 rich) has a similar food-getting mechanism but is not as fastidious 

 about its food as is .1. radians. 



