PROTOZOA AND OTHER ANIMALS 901 



Warren found the ciliate swarming in certain fecal deposits, and 

 then determined that they Hve in the lumen of the liver tubules, some 

 at times passing into the stomach and being discharged in "fecal cham- 

 bers of mucus." The incidence of infection varied from 50 to 87 per- 

 cent at different times of the year, and in one slug 18,000 ciliates were 

 present. What seemed to be the same ciliate was found in the "greenish 

 incrustation of earthy matter underneath bricks and flower pots." This 

 ciliate seemed to have no injurious effect on the slugs, even when present 

 in large numbers. 



Reynolds (1936) observed ciliates in freshly passed feces of the 

 same species of slug in Virginia. He determined these as Colpoda steini, 

 but as he gave no illustration or description, and even made the state- 

 ment that the parasitic stage of this (holotrich) resembles (the hetero- 

 trich) Balantid'tum more closely than it does its own free-living stage, 

 we may not unreasonably consider the systematic status to be unsettled. 

 He determined in sections that the ciliates may be widely distributed in 

 the tissues of the body, and were most abundant in the respiratory 

 chamber and the anterior and posterior ends of the alimentary tract. In 

 one region more than 94 percent of the slugs were infected, in another 

 25 percent. Infection occurred by ingestion, presumably, of the free- 

 living ciliates in the soil, where C. steini was also found. Unlike Warren, 

 Reynolds considered that many slugs are killed by the ciliate, and even 

 suggested that the ciliates may be useful in combating moUuscan pests. 

 Warren had also examined sections, but did not find invasion of the 

 tissues other than the liver tubules. It is likely that the extensive invasion 

 noted by Reynolds would be more harmful to the slugs. 



Probably the ciliate described by van den Berghe (1934) as Glau- 

 coma paedophthora n. sp. belongs in this group of facultative parasites. 

 At any rate, it seems to be a form that has been directly adapted from 

 a free-living habitat to parasitism in the egg masses of Planorbis and 

 Physopsis. At Elizabethville, Belgian Congo, van den Berghe found the 

 ciliates in certain eggs, generally two or three in an egg mass, number- 

 ing from four or five to a great many. They were not found in the 

 genital organs of the snails, and were abundant in the water of the 

 aquarium. Infection of all eggs in a dish took place quickly if ciliates 

 from an infected egg were introduced into the water. In the egg, mul- 

 tiplication from a few ciliates to an intense infection occurred within 

 twelve hours. The embryo was killed by the parasites and within twenty- 



