440 M. R. Lcuckart on rarameciuni ? coli, Malmsten, 



very tough and of considerable thickness, without any other 

 marked characters. It lies upon a clear cortical layer, of no 

 great thickness, which, on its part, encloses the finely granular 

 medullary substance, sprinkled here and there with strongly 

 refractive, small corpuscles. It is only at the anterior extremity, 

 in the vicinity of the buccal orifice and oesophagus, that this 

 cortical layer attains a greater thickness. Here a radiate marking 

 is seen in it, as if a layer of diverging fibres was continued into 

 the margin of the upper lip. Where the oesophagus approaches 

 the granular medullary substance, the latter is drawn inwards, 

 as if furnished with a shallow depression. 



Of internal organs I observed, like Loven, only a nucleus and 

 contractile vacuoles. Tlie former lies on the ventral surface, 

 sometimes further forward, sometimes further back, near the 

 median line. Its outlines are not very sharp; it is pale and 

 finely granular, and of a longish form — not straiglit, but curved 

 somewhat in the form of a horseshoe. The notion of a con- 

 striction is due to an optical illusion, caused by the adjustment 

 of the microscope to the extremities of the nucleus. No nu- 

 cleolus was discovered. Besides the two contractile vacuoles 

 described by Loven, a third is sometimes seen. I have not 

 observed proper contractions in them, although there is no 

 doubt that their contents change, and especially that they are 

 sometimes so much dilated (up to 0'02 mill.) that they push up 

 the external integuments in the form of a hump. On the other 

 hand, however, I have made another astonishing observation on 

 these structures, namely, that they force themselves in the form 

 of drops through the surrounding parenchyma, and thus gradu- 

 ally wander from place to place. 



The length of the Infusoria observed in the pig varies between 

 0075 and 0-11 mill., usually amounting to 0*09 mill., with a 

 breadth of 0*07 mill. 



Their reproduction is unknown to me. Self-division was 

 never witnessed. The only thing which might possibly indicate 

 such phenomena was the occurrence, although but rarely, of 

 spherically contracted unciliated individuals (as large as 0*11 

 mill.), of which the parenchynm possessed a tolerably uniform 

 epake consistence, with the exception of a number of large oil- 

 drops. The cuticle was thickened, and the buccal orifice could no 

 longer be detected, although the anterior extremity of the body 

 was still distinctly recognizable by the thickness of its cortical 

 layer; the presence of tlic horseshoe-like nucleus and of the 

 wandering vacuoles also left no doubt as to the origin of the body. 

 I might almost suppose that the Infusoria in this form quit the 

 intestine of their host in order to propagate externally (by repeated 

 division ?), and finally to migrate again into its (Jesceudants. 



