Dr. C. F. J. Lachmann on the Organization of Infusoria. 117 



the true commencement and termination of their digestive appa- 

 ratus. [With regard to his opinion of its intermediate portions we 

 shall have to speak further hereafter.] In showing that the sup- 

 posed open mouth of the bell-shaped body of Vorticella is closed 

 by a disk [Stirn) set with a circlet of cilia, at the edge of which 

 there is a pit containing the mouth and anus, he only over- 

 looked the projecting seam, which is often even turned back- 

 wards, which surrounds the disk {Stirn) outside the cilia and 

 the pit, and is indicated even by Rosel and O. F. Miiller. To 

 this seam Stein* now again calls attentionf; he calls it the 

 " peristome!," and shows that it is separated by a furrow from 

 the disk bearing the cilia, so that this only forms the upper 

 surface of a " bonnet-shaped " process projecting within the 

 peristome, which he calls the "rotatory organ" [IVirbelorgan) ; 

 on this he distinguishes the upper surface bordered by the cir- 

 clet of cilia as the " disk" (Scheibe), and the lateral walls as the 

 "stem" [Stiel) of the rotatory organ. The Vorticella can re- 

 tract the rotatory organ deeply into the body, and then form a 

 cap-like cover over it by the sphincter- like contraction of the 

 peristome. 



Whilst Ehrenbcrg, in accordance with the idea which he had 

 of the structure of his Pobjfjastrica, supposed he saw an intes- 

 tinal canal proceeding from the mouth, to the sides of wliich 

 vesicular stomachs were attached, and which, being bent into a 

 loop, led back again to the lateral pit on the margin of the bell ; 

 the alimentary tube, according to Stein, is only an inversion of 

 the external membrane, which hangs down into the soft paren- 

 chyma of the body in the form of a short tube, ti-uncated below. 

 The balls of food formed at the end of the oesophagus penetrate 

 through the parenchyma of the body in curves, sometimes de- 

 scribing more than one circuit, and are again thrown out back- 

 wards through the oesophagus : in Opercularia berberina, Stein § 

 [Epistylis berberiformis, Ehrbg.) alone, he saw the balls of excre- 

 ment pass through the lower wall of the throat [Rachen], as he 

 calls the commencement of the oesophagus in the Opercularice, 

 in which it is wider than in most other Vorticellinae, and not 

 through the CEsophagus, and then thrown out. 



* hoe. cit. supra, especially in Die Infusionsthierchen auf ihre Ent- 

 wickelungsgeschichte untersucht, 1854, p. 8. 



t The descriptions and figures of the Vorticellce by Dujardin and Perty 

 are very inexact ; but yet Dujardin's figures indicate the relations of the 

 pai'ts correctly, although, like all his figures of Infusoria, they are very 

 indistinctly and carelessly executed. 



X In the figures it is indicated by a a. 



§ Die Infusionsthierchen auf ihre Entvvickelungsgeschichte untersucht, 

 1854, p. 101. Of Stein's works I shall only quote this book, which is so 

 rich in interesting observations. 



