Protozoan Studies 275 



the bacteria upon which they feed are all precipitated to the outer 

 end of the receptacle. Although the centrifugal force may be 

 such that the Paramoecia can swim against it, the lack of bacteria 

 elsewhere may cause them to remain in the outer end of the recep- 

 tacle in the area made acid by the bacteria. Here some of them 

 are pressed out of shape and may be reduced to thin lamellae. 

 I have seen such forms after being taken from the centrifuge swim 

 about for days in this flattened condition, and sometimes finally 

 regain their normal proportion. More often the Paramoecium 

 turns a number of times while being pressed in the outer end of the 

 receptacle and is reduced to an irregular mass. Such masses 

 may grow to large size and develop several buccal grooves. They 

 may also divide and some of the products of division be irregular, 

 while others form normal Paramoecia. A curious case is shown 

 in Fig. 6, though as this specimen was fed on egg its abnormality 

 is probably as much due to the bulging out of one end by the fatty 

 substance as to the pressure of the wall of the receptacle. Its 

 condition when removed from the centrifuge is shown at a. The 

 large end is three-lobed and it appears as though it were about to 

 divide itself longitudinally into three individuals. The next day 

 there are four lobes on the large end and two on the small end {b). 

 On the third day two of the constrictions have disappeared and 

 the animal is almost divided longitudinally into two. In this con- 

 dition it died. 



One of the irregular individuals taken from the centrifuge and 

 isolated in small watch crystals, divided into two daughters that 

 appeared normal in every respect save that each bore a long horn 

 on the oral side. Dr. H. S. Jennings found a Paramoecium sim- 

 ilar to one of these, in an old culture, and found that for a number 

 of generations (i.e., as long as the series lived) the horn was passed 

 to one of the products of each division and the other was normal. 

 I thought it would be interesting to compare the transmission of 

 these horns produced mechanically, with his observations. The 

 diagram in Fig. 7 presents the results: The irregular individual 

 taken from the centrifuge is represented by a; it divided to form 

 the first two daughters, each with a horn. Some daughters are 

 represented by small sketches, the others by the letters n meaning 



