440 M. Eckhard on the Organization 



muscle still remaining attached to the body, every attempt at 

 complete retraction failed. In neither case had the animal be- 

 come re-attached*. Among the Rotatoria we have an animal 

 analogous to the retracting Vorticella in Conochilus volvox, in 

 which however, independently of the fact that the separate ani- 

 mals in it do not grow upon foreign bodies, but are united toge- 

 ther by their peduncle, the muscle which passes through the 

 muscular sheath divides into three or more bundles, which run 

 separately in the body of the animal and are firmly attached to 

 its internal surface. 



The Vibrions indisputably exhibit the most active movements, 

 but with our present optical resources it is impossible to discover 

 either organs of motion or any muscular structure in them. 



Alimentary Canal. 



5. Most of Siebold's objections to Ehrenberg's views have 

 been made against this part of the subject. In the following 

 remarks I shall consider the individual parts of the alimentary 

 canal in order, and test Siebold's opinions at the proper places. 



1) Mouth. — A mouth has not been directly recognised in all 

 Polygastric Infusoria; still in several of these dubious cases we 

 may with certainty conclude as to its presence, either from 

 alimentary matter being taken internally, or from one to two long 

 cilia which we usually find around a mouth, or from some other 

 circumstance. When distinctly present it forms sometimes a 

 more or less roundish aperture (Paramecium, Enchelys, &c), 

 sometimes a longish fissure (Stylonychia), sometimes a spiral 

 (Spirostomum), sometimes an aperture of some other form. 



Dental structures, in comparison with those of the Rotatoria, 

 in which they occur in such a variety of forms that a treatise 

 might be written upon them alone, are very rare, and can scarcely 

 be observed in any others than in Chilodon, Nassula and Proro- 

 don teres. In these animals the circular oral aperture is inter- 

 nally covered with a ring of longish bristly teeth. According 

 to Ehrenberg, these are forced out of the oral aperture in P. teres 

 by drying the animal f. I have observed this Infusorium once 

 only, and as I was not prepared for this phenomenon I over- 

 looked it ; but I distinctly saw in it the glands (six), which were 

 not then known to him. The peculiar structure of the mouth 



* As far as I know, the influence of the muscle and muscular sheath upon 

 these motions has not been considered. It is therefore to be hoped that 

 when favourable conditions present themselves, such as the injury of one of 

 these parts, they may be taken advantage of in order to ascertain with cer- 

 tainty what share is taken by the muscular sheath and what by the muscle 

 in the rapid contraction. 



f Schriften der Berliner Akademie, 1833, p. 308, and Infusorien, p. 316. 



