28 I'ROTOZOOLOGY 



later from the infection. Recently Janda and Jlrovec (1937) in- 

 jected bacteria-free culture of this ciliate into annelids, molluscs, 

 crustaceans, insects, fishes, and amphibians, and found that only- 

 insects — all of 14 species (both larvae and adults) — became in- 

 fected by this ciliate. In a few days after injection the haemocoele 

 became filled with the ciliates. Of various organs, the ciliates were 

 most abundantly found in the adipose tissue. The organisms 

 were much larger than those present in the original culture. The 

 insects, into which the ciliates were injected, died from the in- 

 fection in a few days. The course of development of the ciliate 

 within an experimental insect depended not only on the amount 

 of the culture injected, but also on the temperature. At 1-4°C. 

 the development was much slower than at 26°C.; but if an in- 

 fected insect was kept at 32-36°C. for 0.5-3 hours, the ciliates 

 were apparently killed and the insect continued to live. When 

 Glaucoma taken from Dixippus morosus were placed in ordinary 

 water, they continued to live and underwent multiplication. The 

 ciliate showed a remarkable power of withstanding the artificial 

 digestion; namely, at 18°C. they lived 4 days in artificial gastric 

 juice with pH 4.2; 2-3 days in a juice with pH 3.6; and a few 

 hours in a juice with pH 1.0. Cleveland (1928) observed Tri- 

 trichomonas fecalis in feces of a single human subject for three 

 years which grew well in feces diluted with tap water, in hay in- 

 fusions with or without free-living protozoans or in tap water 

 with tissues at —3° to 37°C., and which, when fed per os, was able 

 to live indefinitely in the gut of frogs and tadpoles. Reynolds 

 (1936) found that Colpoda steini, a free-living ciliate of fresh 

 water, occurs naturally in the intestine and other viscera of the 

 land slug, Agriolimax agrestis, the slug forms being much larger 

 than the free-living individuals. 



It may further be speculated that Vahlkampfia, Hydramoeba, 

 Schizamoeba, and Endamoeba, are the different stages of the 

 course the intestinal amoebae might have taken during their 

 evolution. Obviously endocommensalism in the alimentary canal 

 was the initial phase of endoparasitism. When these endocom- 

 mensals began to consume an excessive amount of food or to feed 

 on the tissue cells of the host gut, they became the true endo- 

 parasities. Destroying or penetrating through the intestinal wall, 

 they became first established in body cavities or organ cavities 

 and then invaded tissues, cells or even nuclei, thus developing 



