M. R. Leuckart on Paramecium ? coli, Malmsten. 439 



symmetrical, with the buccal funnel and oesophagus in the 

 median line as in a bilateral animal ; whilst in the lateral position 

 of the mouth the outlines of the body present unequal curves, 

 and the buccal funnel and oesophagus ascend asymmetrically to- 

 wards the opposite surface of the body. 



Under these circumstances I have no hesitation in explaining 

 the structure of our animal in accordance with the conditions of 

 the laterally symmetrical type, that is to say, in regarding the 

 mouth as an organ of the median plane. The surface which bears 

 it would then represent the ventral surface ; and the opposite 

 one would have to be regarded as the dorsal surface. The latter 

 is on the whole more strongly arched ; the former, at least in 

 the vicinity of the mouth, is flattened. 



If my view be correct, our parasite can of course no longer 

 remain united with the genus Paramecium (to which it is with 

 doubt referred by its discoverers), as this is distinguished by 

 the lateral position of the mouth. Still less does it belong- 

 to the genus Plagiotoma, to which Claparede and Lachmann 

 have recently referred it, as not the smallest trace of a spiral 

 ciliary furrow exists in our animal. It might perhaps be best 

 and most naturally placed in the genus Holophrya, if we decline 

 for the present to establish a peculiar genus, until we know 

 more of the allied forms (from the colon of the Horse and the 

 paunch of the Ruminants, the latter of which has recently been 

 described by Stein, under the generic name of Isotricha). 



In the median position, the buccal orifice of our parasite appears 

 as a triangular, gaping aperture, with an angle directed back- 

 ward. The anterior side of this triangle belongs to the dorsal 

 surface. It forms as it were a penthouse-like prolongation of 

 this surface — an upper lip, which projects over the mouth and 

 presses down on the ventral surface. The lateral sides or lips 

 project inwards during repose in a curved form into the buccal 

 cavity, whilst in feeding they diverge from the posterior angle. 

 When engaged in feeding, therefore, the buccal orifice has a 

 considerable width (as much as 0'012 mill.), and this the more, 

 as the lips at this time project in a trumpet-like form. 



The buccal orifice is followed by a cavity which gradually 

 dimiuishes, like a funnel, and is at last drawn out into a narrow 

 cylinder — the oesophagus. The buccal cavity, and especially the 

 lips, are covered with cilia, which exhibit a very powerful and 

 almost rotatory movement ; they are perhaps twice as long as 

 the hairs of the otherwise perfectly uniform ciliary coat, and 

 force the food into the interior of the body. In the pig the 

 nutritive matters consist chiefly of a finely granular detritus — 

 rarely of starch-granules. 



The euticula, which covers the body and bears the cilia, is 



