102 rnivcrsify of California Puhlicatioiis in Zoology [Vol. 16 



The anal opening inn., pi. 13. figs. 3, 5) lies at the po.sterior end 

 of the body slightly to the ventral side. It is more easily di.stinguished 

 in a view from the left {an., pi. 13, fig. 3), where it is seen to be con- 

 nected with an anal tiibe {an. t., pi. 13. fig. 3) which extends into the 

 body to a point on the posterior dorsal side of the contractile vacuole. 

 This suggests the idea that the contractile vacuole .stands in connection 

 with the anus through the anal tube. Whether this is really the ease 

 I am unable to say. 



The posterior end of the body around the anal opening is covered 

 with cilia {an. cil.. pi. 13. figs. 2. 3, 4). In length these .stand between 

 tho.se of the dorsal ciliary zone and the adoral membranelles, on the 

 one hand, and the oral membranelles and the cilia of the gullet on the 

 other. 



Reproduction, so far as I have ob.served. is by transverse fission, 

 one stage of which is shown in figure 4. in which the micronucleus has 

 divided and the new cullet and oral region are forming. 



Observ.vtions on the Living M.\teri.\l 



Observations on the living animals made under conditions as nearly 

 normal as possible show that they travel at a rate of speed less than 

 that of the other eiliates from the caecum of the horse. The normal 

 course taken by this animal in forward movement is not in a straight 

 line, but is more or less that of a spiral, with frequent turnings about 

 the long axis of the body. This turning is due in part to the asym- 

 metrical arrangement of the adoral membranelles and in part to the 

 curvature of the anterior process. 



The movement of the adoral membranelles is wave-like, beginning 

 at the extreme anterior end of the zone and extending slowly along its 

 whole length to the posterior end. 



The cuticle shows clear and transparent, with no striations. Ecto- 

 plasm and entoplasm are clearly defined, the latter much darker in 

 color and filled with fine particles of food. At certain levels the 

 maeronueleus and micronucleus can be easily distinguished, the macro- 

 nucleus having a grayish granular appearance and the micronucleus 

 appearing as a bright, round, more highly refractive body. The con- 

 tractile vacuole shows up very clearly in the living animals. The 

 contractions are regular; but in.stead of being sudden, as in Parame- 

 cium, are slow and more of the nature of true pulsations. 



