PROTOZOA AND OTHER ANIMALS 979 



(1933), who compared it with milk feeding, is the one discovered by 

 Becker (1929). Becker starved his animals for three days, then gave 

 two doses, twenty-four hours apart, of fifty cc. of 2-percent copper sul- 

 phate, passed through a rubber tube into the rumen. Strelkow et al. 

 shortened the starvation period to one day and gave three doses of 

 copper sulphate, thus shortening the defaunation period to three days. 



The ciliates take up plant fragments in the rumen, and Trier (1926) 

 stated that they are apparently exclusively plant feeders. Bacteria, flagel- 

 lates, amoebae, and ciliates may also be ingested, however. According 

 to Dogiel (1925), no Ophryoscolecidae are entirely predatory, as plant 

 debris is always to be found in the plasma. Kofoid and MacLennan 

 (1930, 1932, 1933) and Kofoid and Christenson (1934) recorded the 

 food contents of most of the species they studied, and showed clearly 

 that food habits differ. Some appear to feed only on bacteria and other 

 Protozoa, especially small flagellates. Others use various combinations of 

 plant and animal material, some only plant material, and bacteria with 

 plant debris are ingested by a large proportion. Some species are more in- 

 clined than others to be predatory on ciliates. Entodinium vorax, accord- 

 ing to Dogiel ( 1925 ) , almost always contains the remains of one or more 

 smaller Entodinium. 



The plant material is often in relatively small particles, but some 

 ophryoscolecids take in large pieces that may distort the body. Dogiel 

 (1925) described how Diplodinium gracile may seem actually to tear 

 away fibers (Fig. 206A, B); Opisthotrichum janus may bite from the 

 surface of a plant piece the remains of ruptured tissue (Fig. 206D); 

 and D. bubalidis, D. medium, and D. maggii may devour large irregular 

 or flat grass pieces (Fig. 206C), but not fibers. Ostracodinium sp. can 

 take in and roll up large cellulose fibers (Weineck, 1934). 



Green plant fragments are taken in preference to non-green ones, 

 according to Usuelli (1930b), who ofl^ered a choice by feeding hay and 

 barley. A third to a half of the green fragments were in about half of 

 the ciliates; whereas less than 10 percent of them took in non-green 

 fragments, all but a few of which remained free in the lumen. For 

 this selectivity, Usuelli contended, the softer, smoother characteristics 

 of the green plant pieces are responsible. 



When available, starch grains are ingested avidly by the ciliates, both 

 in the rumen and in the thermostat. Four hours after giving a sheep 



