PARASITES OF PROTOZOA 1093 



cytoplasm by dissolution of the earlier common plasma mass. Borgert 

 regarded these bodies as parasites of the radiolaria, unrelated to Amoe- 

 bophrya. Tliough probably it is only an analogy, certain features in their 

 development suggest the life history of Sphaerita. 



It appears from statements by Neresheimer (1904, 1908) that Amoe- 

 ba phrya is not restricted entirely to Radiolaria. Doflein, he wrote, showed 

 him preparations of Noctiluca miliaris in which the parasite was present. 



Metazoa 



A number of rotifers live attached to other animals as ectocommensals 

 or ectoparasites. Ehrenberg (1838) found Proales petromyzon (Ehrbg.) 

 and its eggs attached to the branched vorticellids Epistylis digitalis, Car- 

 chesium polypinum, and Zoothamnium geniculatum, and stated that it 

 devours the vorticellid. Wesenberg-Lund (1929) showed it and its 

 eggs on Zoothamnium. It is a predator rather than a parasite, but differs 

 from ordinary predators in its attachment. Hudson and Gosse (1889), 

 however, found it always free, though often in close association with 

 Epistylis and Carchesium. 



Approaching closer to parasitism are certain species of Proales, which 

 live in certain algae and Protozoa. P. iverneckii (Ehrbg.) occurs rather 

 commonly in galls on Vaucheria; P. parasita (Ehrbg.) is parasitic in 

 Volvox; and P. latrunculus Penard invades the heliozoan Acanthocystis 

 turfacea. 



Proales parasita was found by Ehrenberg (1838) and Cohn (1858) 

 in Volvox. Plate (1886) described Hertwigia volvocicola from Volvox 

 globator, considering this to be a different species from the preceding. 

 It is listed as a synonym of P. parasita by Hudson and Gosse (1889), 

 but Wesenberg-Lund (1929) considered it again as a separate species. 

 Whether different or not, the habits of the forms are the same. They 

 swim about within Volvox coenobia and feed on the cells. The males 

 live only a day or two, remaining entirely within the host in which they 

 are hatched. The females may be found within or outside the coenobium. 

 Eggs are laid in the host, where they hatch and, according to Hudson 

 and Gosse, the young rotifer either enters a daughter colony and is 

 expelled with it or emerges to swim free. Hudson and Gosse stated that 

 "Volvox appears to suffer little from the depredations of its ungrateful 

 guest." 



