390 Dr. R. Greef on the Structure and 



These form-constituents, which remain after the removal of 

 the larger food-balls, are, moreover, in some species, of very 

 constant form and size : for example, in Ejn'sti/lis Jlavicans they 

 consist of shining, light-yellow spherules, of which usually 

 three or four, but often several, are massed together into com- 

 paratively large balls (PI. XV. fig. 5), so that one is induced 

 to regard the whole of the fluid, now freed from the coarser, 

 still undissolved or insoluble nutritive materials, as the blood 

 or chyle mixed with water. 



The preceding observations and indications may for the 

 present suffice for the establishment of my assumption of a 

 digestive body-cavity in the Vorticellse ; and we now come 

 to the second of the questions raised above, namely the nature 

 of the alimentary tube leading into this digestive cavity. As 

 has been already remarked, the connect position of the external 

 orifice of the nutritive tube described by him as the mouth, as 

 also the position of the anus, was first recognized by Ehren- 

 berg. According to him the rounded buccal aperture lies di- 

 rectly behind the ciliated disk, and the anus in a pit in the initial 

 portion of the nutritive canal which enters the body. Stein 

 showed further that this buccal opening is situated between 

 the ciliated disk and the peristome, and that from this point 

 the nutritive tube, distinguished by him into pharynx and oeso- 

 phagus, hangs down into the body. The food-balls were sup- 

 posed to be pushed through the oesophagus into the parenchyma 

 of the body, and in most cases the exhausted food to be carried 

 back again in the same way. The most accurate description 

 of the nutritive apparatus of the Vorticella3 was given by Lach- 

 mann*. He found that the cilia upon the anterior disk of the 

 body took a spiral course, and, indeed, that in Carchesium 

 polT/jnuunij for example, this ciliary spiral commenced to the 

 right of the external nutritive aperture called the mouth by 

 Ehrenberg and Stein, and then turned away to the left over 

 the latter and ran round the margin of the circular disk, to 

 sink again at last into the buccal aperture and into the first 

 portion of the alimentary canal (see PI. XIV. fig. 9). At the 

 bottom of this first portion (as Ehrenberg had already dis- 

 covered) the anus was situated, for which reason the mouth in 

 reality could only commence here. The initial portion, situ- 

 ated before this point, and including Ehrenberg's buccal aper- 

 ture, was therefore described, after the example of Johannes 

 Miiller, as the porch of the digestive apparatus, the vestibulum. 

 The vestibulum was continued into a thinner, short tube, the 

 cesophagiis^ and terminated in a somewhat wider, spindle-shaped 

 part, which was called the pharynx^ through which the par- 

 * Mtaier's Archiv, 1850, p. .340. 



