72 PROFESSOR O. BUTSCHLI. 



bodyj near the base of the flagellum within the collar. The 

 process of ingestion of food has not yet been fully followed 

 out. By careful observation, however, a vacuole-like struc- 

 ture (fig. 7 a, x) is seen to project upon one side of the body 

 close below the base of the collar, and beyond the contour of 

 the body. Soon this structure disappears, and after a cer- 

 tain time another similar one appears upon the opposite side. 

 It has also in some measure the appearance of wandering 

 about close under the base of the collar ; but it is not yet 

 known whether this really happens, or whether diiFerent 

 vacuoles rise and then vanish in opposite parts of the 

 body. The whole matter, however, becomes simple, if 

 it be assumed that the vacuole changes its position. 

 The ingestion of food takes place into the middle of 

 these vacuoles in the following way : — Particles of various 

 kinds — Micrococci, Bacteria, &c. — are often driven by 

 the movements of the flagellum on to the outer surface of 

 the collar, to which they adhere ; occasionally the entire 

 outer face of the collar is seen to be covered by such ad- 

 herent particles. Gradually all the particles are seen to be 

 pushed backwards, first on to the collar, and a little later to 

 the base of the collar, until they touch the vacuole, by which 

 they are taken up and engulphed as food for the body. The 

 remnants of the food are extruded close to the base of the 

 flagellum within the collar. 



The nucleus situated near the anterior end is first seen 

 within the body, it consists in the living state of a transparent 

 portion containing dark bodies. The nucleus becomes much 

 more prominent after treatment with acetic acid, but there 

 still remains the dark and somewhat granular case and 

 the transparent exterior. The protoplasmic body is very 

 frequently filled with a number of large non-contractile 

 vacuoles in addition to the food vacuoles. These large 

 vacuoles can only be distinguished from one another by their 

 boundary walls, which are comparatively very delicate ; 

 hence the whole organism appears to be a large alveolar 

 vacuole. The contractile vacuoles are always double, and 

 lie at the posterior end of the body on opposite sides, not 

 quite in the same section, since one is generally a little in 

 advance of the other, nearly in the centre of the body's length. 

 No third contractile vacuole was observed by Biitschli, 

 although one has been described by Clark. The two 

 vacuoles contract alternately ; their contraction is very slow. 

 The formation of the vacuole is peculiar, and has analogies 

 with the same process in such ciliata as Uroleptus. The 

 mode is as follows : — A narrow-elongated space filled 



