Natural History of the Vorticellse. 393 



cans J two valve-Uhe jpafrtitions (PI. XVI. fig. 2, X; &^'), which 

 occur in the posterior cavity of the oesophagus, the true pharynx, 

 and which, aided by the corresponding ciliation, determine the 

 direction of the two opposite currents. 



From the cesophagus, or, if it be preferred, the vestibulum, 

 the alimentary canal is continued as already described, making 

 a curve and running, backwards and towards the ventral 

 side, in a tube furnished with proper walls and gradually be- 

 coming narrower, which then finally, according to observations 

 up to this time, passes into a portion which is a little widened 

 anteriorly and pointed posteriorly, and here terminates. In this 

 terminal portion the food diiven by the ciliary current into 

 the digestive apparatus, is collected into a ball, and then pushed 

 directly into the parenchyma of the body. This part of the 

 alimentary apparatus from the issue of the vestibulum [i. e. from 

 the inner buccal opening) to the spindle-shaped terminal portion, 

 was called by Lachmann the oesophagus, and only the ter- 

 minal portion itself the pharynx ; whilst Stein names the 

 whole from the vestibulum, and therefore both the oesophagus 

 and pharynx of Lachmann, the pharynx. According to the 

 above statements with regard to the desirability of the deno- 

 mination " vestibulum " for the initial portion, if we should 

 give the name of pharynx to this latter, the above-described 

 terminal portion must of course be regarded as the oesophagus. 



But let this be as it may (as in it we have to do rather with a 

 more or less desirable conception and terminology than with 

 actual observation) , the results of investigations up to this time 

 all agree to show that behind this spindle-shaped dilatation of 

 the pharynx or oesophagus there is no trace of special food-pas- 

 sages, but that the digestive canal here fully comes to an end. 



JSTevertheless, notwithstanding the careful investigations of 

 Lachmann and Stein relating to this point, I must affirm, from 

 my own observations, that, at least in Epistylis flavicans^ this 

 supposed terminal portion is really continued for a considerable 

 distance further into the body-cavity as a closed canal with 

 proper walls. 



Of this we may convince ourselves in two ways : — first, by 

 the direct observation of the canal in question within the body- 

 cavity, nay, even by isolating it ; and secondly, by subjecting 

 the animal to a colour-diet, so as to trace the course taken by 

 the coloured [i. e. the food) particles. Let us first of all take 

 up the former as the direct and most certain course, and em- 

 ploy the second, which has been already so often tried and 

 which so easily leads to delusions, only for the completion of 

 our researches. 



When a colony of Emstylis Jlavicans has been kept for a 

 Ann. 6b Mag. N. Hist. Ser.4. Vol. hi. 27 



