STUDIES ON SPATHIDIUM SPAIHULA 197 



be induced to conjugate.-- Moody's amicronucleate race is un- 

 doubtedly comparable with the amicronucleate races of various 

 ciliates recently described by Dawson, -^ Landis,^* Woodruff," 

 and Patten. 26 



FEEDING BEHAVIOR 



Spathidium is one of the so-called hunter ciliates, employing 

 for food the smaller ciliates which it captures during its peri- 

 grinations. Maupas, in his study on the life-history of Infusoria, 

 carried for a short time a culture of this organism which he fed 

 chiefly on Glaucoma, Cyclidium, and Cryptochilum. Moody 

 found it impossible to conduct her long pedigree culture without 

 Colpidium for food and definitely states that she never saw any 

 other ciliates paralyzed or eaten. The animals of our culture 

 readily paralyze and swallow almost any small ciliate with which 

 they come in contact, though flagellates of various kinds are 

 immune. As a matter of fact, however, we have employed 

 chiefly species of Colpidium for food because they can be de- 

 veloped for the purpose in countless numbers so readily in small 

 flasks of hay infusion. 



Spathidium typically swims forward quite rapidly through 

 the water, revolving on its long axis, and gives at first glance 

 the impression that it is exploring its path with its truncated 

 anterior end. This appearance results chiefly from the fact 

 that the axis of revolution does not pass directly from posterior 

 to anterior end, but leaves the body a short distance posterior 

 to the mouth region. Accordingly, the narrower anterior end 

 traces the circumference of a circle of greater diameter than 

 the rest of the body, especially when the animal is swimming 



22 L. L. Woodruff and Hope Spencer, The early effects of conjugation on the 

 division rate of Spathidium spathula. Proc. Soc. for Exper. Biol, and Medicine, 

 1921, 18. The survival value of conjugation in the life history of Spathidium 

 spathula. Ibid, 1921, 18. 



23 J. A. Dawson, An experimental study of an amicronucleate Oxytricha. 

 I, Jour. Exp. Zool., 1919, vol. 29, p. 473. II, ibid., 1920, vol. 30, p. 129. 



24 E. M. Landis, Amer. Naturalist, 1920, vol. 54, p. 453. 

 26 L. L. Woodruff, Jour. Exp. Zool., 1921, vol. 34, p. 329. 



26 M. W. Patten, Proc. Soc. for Exper. Biology and Medicine, 1921, vol. IS, 

 p. 188. 



