976 PROTOZOA AND OTHER ANIMALS 



Several attempts have been made, with varying results, to estimate 

 the reproductive rate by counting dividing ciliates. No adequate deter- 

 mination has been made of the rate of reproduction in a day, a calcu- 

 lation which cannot be based only on the amount of fission seen on one 

 occasion. Rate of reproduction in culture, furthermore, at least in the 

 absence of completely satisfactory culture methods, is not necessarily 

 the same as that in the rumen. Mowry and Becker (1930) found in 

 goats usually less than 0.5 percent of dividing forms, and never as many 

 as one percent. Ferber and Winogradowa-Fedorowa (1929) found in 

 a ram on different occasions from 0.9 to 15 percent in division, the aver- 

 age being 7 percent. Examinations were made twice a day, but they 

 failed to note, as Mowry and Becker pointed out, that from observation 

 of 7 percent dividing forms in two samples per day, it does not follow 

 that 7 percent of the ciliates are dividing in a day. The rate of multipli- 

 cation would probably be much higher than that. Westphal (1934a) 

 found that in culture of certain forms each ciliate divided an average of 

 once in fourteen hours, and the population became 3-fold in a day. It 

 reached in more dilute medium a rate of 5.8-foId in twenty-four hours. 

 Dogiel and Winogradowa-Fedorowa (1930) published a report that 

 from 50 to 90 percent of the ciliates were observed in division in goats 

 under normal conditions of nutrition, and from 12 to 50 percent in 

 slaughterhouse oxen. Westphal (1934a) calculated that there must be 

 daily at least a quadrupling of the number of ciliates. 



Rumen ciliates live in a chemically complex and delicately balanced 

 environment, and in vitro culture has been a difficult problem. Becker 

 and Talbott (1927) and earlier workers failed to obtain more than 

 limited survival. Knoth (1928) obtained longer survival in a medium 

 of rumen fluid, with controlled pH, and with partly anaerobic condi- 

 tions provided by a mixture of carbon dioxide and methane, the maxi- 

 mum being the life of Entodinium. with daily change to fresh solution, 

 for five days. Margolin (1930), in media of hay infusion with rice 

 starch and filter paper acted on by cellulose-decomposing bacteria, the 

 pH being kept at 6.8, reported maintenance of cultures for twenty-four 

 days; but others have been unable to use his methods successfully 

 (Becker, 1932; Westphal, 1934a). Westphal (1934a, 1934b) reported 

 real success with a medium of rumen fluid kept under anaerobic con- 

 ditions, with urea and starch added. There was active multiplication in 



