1094 PARASITES OF PROTOZOA 



Penard (1904, 1908-9) has given the most complete account of 

 Proales latrunculus, certain observations on which had been made by 

 Archer (1869), Leidy (1879), and Stokes (1884). Penard studied an 

 epidemic outbreak of the parasite, which eventually carried off most of 

 a group of the Heliozoa. He stated, however, that it is rare, in the sense 

 that many Acanthocystis turfacea in various localities may be examined 

 without encountering it. It is widespread geographically, as indicated 

 by the records from Switzerland, England, and the United States. 



After being introduced into the body of Acanthocystts, probably, 

 according to Penard, by being ingulfed as prey, the rotifer moves about 

 actively in the cytoplasm. It devours the zoochlorellae and the substance 

 of the heliozoan. In two or three hours an egg may be laid, after which 

 the rotifer may continue to feed and lay a second, smaller egg. The 

 heliozoan occasionally frees itself of the invader, but usually it perishes 

 before the end of the first day. After laying its eggs, the rotifer escapes 

 by an orifice in the then empty envelope of spicules — empty, that is, 

 except for the few small eggs. The young rotifers develop rapidly, 

 hatching in two or three days, when they leave by the orifice through 

 which the parent escaped. 



As Penard (1908-9) remarked, these rotifers are not true parasites, 

 as they are not adapted to continuous existence in their host. They behave 

 rather as predaceous forms which consume the host from within. One 

 notes a marked specificity to certain hosts or related hosts in the rotifers 

 ectozoic on colonial vorticellids and those endozoic in V ciucheria, Volvox, 

 and Acanthocystis. 



Ehrenberg (1888) on one occasion found the usually ectozoic P. 

 petromyzon within Volvox globator; and Wesenberg-Lund (1929) stated 

 that Volvox contained also species of Diglena, rotifers that are naturally 

 free-living. 



Living nematode worms have occasionally been encountered in Pro- 

 tozoa. It is not known whether this ever represents obligatory parasitism, 

 or is only an invasion by accidentally or facultatively parasitic forms. 

 Wesenberg-Lund (1929) stated that free-living nematodes have been 

 found in Volvox; and Schubotz (1908) wrote that Hartmann informed 

 him of having seen nematodes in that flagellate. Schubotz found as many 

 as three nematodes in approximately a tenth of Fycnothvix nionocystoides 

 from Procavia capensis. He stated that for entry into this large ciliate, 



