394 Dr. K. Greef on the Structure and 



time isolated in clear water, the food-balls circulating in the 

 body-cavity are all, as already stated, gradually expelled 

 through the anus. By this means the animals, which are 

 otherwise of a yellow or yellowish-brown colour, become paler 

 and more transparent, and render it possible to get a better 

 insight into the interior space of the body. When a Vorti- 

 cellan thus prepared is examined under careful compression 

 and in a suitable position, we see clearly in the first place the 

 course of the whole of the above-described alimentary appa- 

 ratus from the buccal aperture (PI. XVI. figs. 1 & 2,m), through 

 the vestibulum (pharynx) and the oesophagus (figs. 1 & 2, o), to 

 the spindle-shaped terminal portion {v), and at the same time 

 that the whole of this passage is clothed with briskly striking 

 although comparatively few cilia. The end of this canal, how- 

 ever, the spindle-shaped dilatation which has been repeatedly 

 mentioned, is, mEpistylis flavica7iSj not as represented by Lach- 

 mann and Stein and as appears to be the case in most other 

 Vorticellge, a simple continuation of the canal preceding it (the 

 oesophagus), but it presents itself as a bellied funnel distinctly 

 marked qf'tiom the latter (PI. XVI. figs. 1 &2,v), which em- 

 braces the end of the canal opening into it, and the posteriorly 

 directed point of which, as may be most distinctly seen under 

 favourable circumstances, passes into a Jine canal (figs. 1 & 

 2, d) , which describes a broad curve in the bottom of the body- 

 cavity and suddenly breaks off, i. e. opens freely into the body- 

 cavity, on the side opposite to the funnel and about at the level 

 of its commencement. The whole canal, from the point of the 

 funnel to its termination, when not dilated by nutritive ma- 

 terial or water, is more or less collapsed, and consequently, in 

 this state, appears as a clear curved line or fine streak. Some- 

 times by carefully and gradually compressing the body until 

 it is crushed, at the same time keeping the clear curved line 

 uninterruptedly in view, we may succeed in recognizing and 

 tracing it for a certain distance in the effluent contents, which 

 are quite out of their natural position. This phenomenon, 

 however, which is therefore to a certain extent equivalent to 

 an isolation of the part under consideration, is, I think, decisive, 

 as it can only be explained by the presence of an actual canal. 



After this direct observation, which may certainly often be 

 attended with great difficulties and by frequent failure, with 

 much loss of time caused by constant repetitions, we may con- 

 firm and complete the picture thus obtained in the most beau- 

 tiful manner by administering a carmine diet to our animal- 

 cules, but at the same time meet with new difficulties in the 

 way of this conception. 



We see, in the first place, how the particles of carmine are 

 carried by the circles of cilia of the ciliated disk towards the 



