PARASITES OF PROTOZOA 1035 



a testis (the chromosome filaments having been mistaken for sperma- 

 tozoa). Engelmann (1862), finding these parasites in nuclei of Para- 

 mecium caudatum and Blepharisma lateritia, nevertheless continued to 

 regard them as spermatozoa; but Engelmann (1876) wrote of bacteria 

 parasitic in nuclei of Stylonychia 77iyUlu5. Biitschli (1876), severely 

 criticizing the Balbiani-Stein hypothesis of sexual reproduction, reported 

 rods in the nucleus (macronucleus) of P. aurelia, and agreed with Balbiani 

 that they are parasites. He remarked that similar parasites are sometimes 

 found in the nucleolus (micronucleus) of many Infusoria. A review of the 

 earlier observations is given by Biitschli (1889, p. 1828). 



Balbiani (1893), giving a figure and a brief discussion of parasites 

 in the macronucleus of Stentor polymorphus, remarked on the fact that 

 the parasitized animal appeared to be perfectly normal and continued 

 its ordinary functions. Zoochlorellae were neither more nor less abundant 

 than usual. The alteration of the nucleus might seem to be equivalent 

 to its artificial extirpation, as the nuclear substance had completely or 

 almost completely disappeared. He discussed these facts in connection 

 with his experimental results in the removal of the macronucleus, and 

 concluded that they were not in disagreement. A minimal amount of the 

 nuclear substance might still have been present and sufficed; or the 

 animal observed might have been in the limited period during which 

 normal life continues. 



Studies of the nuclear parasites of 'Paramecium and their effects on the 

 animal were made by Hafkine (1890), Metschnikoff (1892), and 

 Fiveiskaja (1929); and certain observations on the consequences of 

 parasitism were reported by Bozler (1924). A similar parasite, studied 

 in detail by Petschenko (1911), was believed to be cytoplasmic. This 

 author stated that the possibility of confusing microorganisms which 

 live in the micronucleus with those that live in the cytoplasm cannot 

 be denied. 



Hafkine distinguished three species of Holospora. H. undulata in- 

 vades the micronucleus and is spiraled. At the beginning the organism 

 is a small, fusiform corpuscle. The second species, H. elegans, occurs 

 also in the micronucleus, but is never associated with the first. The 

 vegetative stage is fusiform and more elongated and slender than the 

 others. The third species, H. obtusa, invades the macronucleus. It is 

 not spiraled and the two ends are rounded, instead of both or one 



