1914] Sharp: Diplodinium ecaudatum 97 



ecaudatum in any one stomach certain groupings of forms seemed to 

 be the rule ; that is to say, we have here a general condition in which 

 (a) forma ecaudatum may be the only form present, (6) forma cau- 

 datum may be the only form present, (c) forma ecaudatum and forma 

 caudatum may be present in about equal numbers, {d) forma quadri- 

 caudat'um may be the only form present, (e) forma quadricaudatum 

 may be associated with any or all of the other forms. In other words, 

 almost any combination may exist, with this exception — the forms 

 Mcaudatum, tricaudatum, and cattanei have never been found except 

 in the presence of the forma quadricaudatum. 



As noted above, under technique, satisfactory observations of the 

 activities of the living animals could be obtained only by reducing the 

 temperature a few degrees, which reduction and control was made 

 possible by the automatic constant-temperature oven to which refer- 

 ence has been made. In this oven at a temperature of about 30° C, 

 the following observations were made, for at that temperature, al- 

 though only 5?5 C. below normal, the restless activities of the mem- 

 bers of this species are slowed down sufficiently to permit of satis- 

 factory study. 



The cuticle shows clear and transparent, the skeletal areas are 

 easily defined; in fact these areas are much more plainly seen in the 

 living animals than in the fixed material. The boundary layer be- 

 tween ectoplasm and entoplasm is very clearly marked off, and at 

 certain levels the macronucleus and the micronucleus can be easily 

 distinguished, the macronucleus having the characteristic granular 

 appearance and the micronucleus appearing as a bright, shining little 

 body, refracting the light strongly. The contractile vacuoles show 

 up much more clearly in the living animals than they do in the fixed 

 material. These contractile vacuoles do not contract suddenly and 

 disappear as in the case of Paramecium, but, on the contrary, contract 

 slowly and only slightly, then gradually enlarge to their former size. 

 Their action is more of a true pulsation. The caecum and rectum 

 may be distinguished just before and during the process of defecation. 

 In a few cases this process has been observed. 



The streaming of the entoplasm referred to previously may usually 

 be observed during quiescent periods in the animal's locomotor activity. 

 For purpose of description this streaming may be roughly divided 

 into three main currents, according to the general direction assumed 

 by each: (1) a peripheral posterior current, (2) an anterior current, 

 and (3) an internal posterior current. (1) The direction of the 



