PROTOZOA AND OTHER ANIMALS 947 



had one or more species of Astomata; three-quarters of 2,062 individ- 

 uals were infected. Some hosts have several species of the ciiiates; in 

 one there are as many as 7, but all may not be present at the same time. 

 Heidenreich (1935) examined worms, mostly oligochaetes and turbel- 

 larians, collected in the vicinity of Breslau. He noted that very few 

 ciiiates are found in worms from flowing water, presumably because 

 of the fact that cysts are carried away. 



There is a certain amount of host-specificity in the group. Hoplo- 

 phryidae and Intoschellinidae appear to be restricted to annelids. Many 

 species have been described from one host only, but some occur in many 

 hosts. Cheissin (1930) found Radio phrya hopUtes Rossolimo and Mes- 

 nilella rostrata Rossolimo in most of the Lumbriculidae; the former oc- 

 curred only in worms of that family, the latter was found also in an 

 enchytraeid. There has been a high degree of differentiation of species 

 and genera in the Astomata, although there are comparatively few char- 

 acteristics in which that differentiation can be exhibited. 



There are two large groups of the Astomata from annelids, those with- 

 out and those with skeletal structures. The former constitute the family 

 Anoplophryidae; the latter were put by Heidenreich (1935) into the 

 two families Hoplitophryidae and Intoshellinidae. The skeletal struc- 

 tures are differentiations of the ectoplasm or endoplasm, or of both, in 

 the form of resistant, retractile, and stainable rods, hooks, rays, or fibrils. 

 They are completely renewed at division. According to the scheme of de- 

 velopment outlined by Heidenreich, the simplest form is a small, ecto- 

 plasmic, skeletal plate with a short tooth that scarcely extends from the 

 pellicle [Eumonodontophrya kijenskiji, Fig. 202K). The plate elon- 

 gates to the rod- like spicule characteristic of Ho plho phrya, in some 

 species of which there is a point projecting from the anterior end of the 

 body. In H. fiss/spkulaia (Ch.) [=Protoradw phrya fiss/spkulata Cheis- 

 sin) the spicule is divided in a narrow-angled cleft in its posterior part. 

 This is an approach toward the V-shaped ectoplasmic skeletal element 

 of Radiophrya (Fig. 202 C). The latter is usually provided with an 

 apical point, which projects from the body surface (Fig. 202, J). Some- 

 times a second element, a hook or tooth attached to the central, basal part 

 of the arrowhead and projecting free of the body, is present. This 

 pointed tooth typically projects backward at an angle. In R. hoplites, 

 Cheissin (1930) observed that the tooth is capable of movement. There 



