914 PROTOZOA AND OTHER ANIMALS 



nata (Penard, 1922), and that of E. nehulosa Entz to Cothurnia is ap- 

 parently obligatory predatism; this relationship, of course, is comparable 

 to parasitism, as, if the host were a metazoan and were only partially 

 destroyed by the attacks of the ciliate, we would doubtless consider the 

 latter a true parasite. 



Haematophagus megapterae Woodcock and Lodge and Metacystis 

 megapterae Kahl are commensals on the bristles of the whale Megaptera 

 nodosa (Kahl, 1930). 



A number of pleurostomatous and hypostomatous gymnostomes have 

 become associated with animal hosts. In the former group there is 

 Amphileptus claparedei Stein, "parasitic on the stalks of colonial Vor- 

 ticellidae" (Kahl, 1933); and A. carchesii Stein in a similar situation. 

 Edmondson (1906) reported that after feeding upon a zooid the latter 

 species (discussed by him as A. meieagris Ehr.) attaches itself to a stalk. 

 He found that many were present on Carchesium polypiniwi, clasping 

 the stalks by a deeply cleft posterior end. In addition to these more or 

 less predatory species, there is Lionotus branchiarum (Wenrich) Kahl, 

 described by Wenrich (1924b) as A. hranchiarum. It is a true parasite 

 on the gills of the tadpoles of several species of Rana, where it lives in a 

 capsule under the cuticular membrane and occasionally detaches and en- 

 gulfs gill cells. Wenrich (1935) discussed the possibility that A. 

 branchiarmn is transitional between a predatory and parasitic status. 

 There is a predaceous, free-swimming phase on the surface of the gills 

 by which other Protozoa may be devoured. Three species of Lionotus, 

 L. impatjens Penard, L. asell'i Kahl, and L. hinmdi Penard are com- 

 mensal among the gills of Asellus; and one, L. agilis Penard, occurs on 

 the ventral surface, among the legs, and on the egg masses of Cyclops. 

 The pleurostome genus Branchioecetes Kahl is very closely related to 

 Loxophyllum, in which Svec (1897) and Penard (1922) put the spe- 

 cies. The two species B. aselli (Svec) and B. gammavi (Penard) are 

 commensals on their hosts, to which they adhere by thigmotactic cilia. 



Commensal hypostomes belong to the genera Trochilia and especially 

 Chilodonella. Trochilia [Dysteropsis) mimita (Roux) has been found 

 free-living as well as commensal with Cyclops, Gammarus, and Asellus 

 (Penard, 1922). Commensalism is widespread in Chilodonella, several 

 species of which are apparently obligatory commensals on fish, others on 

 certain rotifers, amphipods, and isopods. The species on the gills of fish 



