308 GENERAL HISTORY OF THE INFUSORIA. 



Opercularia (as circumscribed by Stein) and Lagenophrys, Stein ; in tlie two 

 latter the vestibulum is very wide, whilst in the elongated species it is narrow, 

 but generally possesses a deep excavation for the anus." 



'' Besides the cilia of the spiral (cihary wreath), some stronger cilia also 

 stand in the vestibulum, in front of the mouth ; these do not take part in 

 the regular activity of the others, but only strike forcibly sometimes, — appa- 

 rently to remove from the vestibulum coarse substances which may have got 

 into it, and also the masses of excrement." 



" The morsel passed from the pharynx into the interior of the body runs 

 nearly to the posterior extremity of the Vorticella, and then, turning upwards, 

 rises on the side of the body opposite to the pharynx. Duiing this portion 

 of its course, it usually still retains the spindle-shape communicated to it by 

 the pharynx, and only here changes to the globular form, often rather sud- 

 denly : this induced me at first to think that the morsel was still enclosed in 

 a tube during this part of its course ; and this opinion seemed to be supported 

 by the cii'cumstance that, before and behind the morsel, two lines are not un- 

 frequentiy seen, which unite at a short distance from it, like the outlines of 

 a tube which it has dilated. Subsequent observations, how^ever, have again 

 sho^Ti me that this opinion is an improbable one ; for the circumstances de- 

 scribed must also occur when a fusiform morsel is passed wdth some force and 

 rapidity through a quiescent or slow-moving tenacious fiuid mass : the above- 

 mentioned lines, before and behind the morsel, must be produced by the se- 

 paration and reunion of the gelatinous mass, even if the morsel is not sur- 

 romided by a tube. But the existence of a tube depending from the pharynx 

 appears also to be directly contradicted by the fact, on the one hand, that the 

 curves described by the morsel are sometimes larger and sometimes smaller, 

 and on the other, that the morsel acquires the globular form sometimes sooner 

 and sometimes later, according as it is pushed out of the j^harynx with greater 

 or less force and rapidity. The masses v*^liirled into the pharynx are not 

 always aggregated into a morsel ; but sometimes, under conditions which 

 have not yet been satisfactorily ascertained, all the masses which reach the 

 pharynx are seen to pass quickly through it without staying in it ; they then 

 stream through the mass surrounding them in a clear streak which, like the 

 morsels, describes a curve at the bottom- of the bell, and only mix with the 

 mass when their rapidity of motion has diminished. A roundish morsel, which 

 might be regarded as a fiill stomach, is then never formed. We might easily 

 be inclined to regard the clear bent streak wdth the particles flowing in it as 

 an intestine ; and this has probably been done by Ehrenberg, who states that 

 he distinctly saw the bent intestine in some VorticeUina, especially in Epi- 

 stylis plicatilis, in which I have also been able to study the phenomenon very 

 closely. But in this case also there are the same reasons against the sup- 

 position of an intestinal tube, as in that of the lines appearing before and 

 behind a fusiform mass : here likewise, not only the form, but also the length, 

 of the curve varies : whilst at one time it is but short, and soon terminates 

 by the intermixtiu"e of the particles contained in it with the suiTounding 

 mass, it may immediately afterwards be twice as long or longer — it may even 

 make a complete circuit and return nearly to its point of commencement be- 

 neath the pharynx- — a variation which appears only to depend upon the force 

 with w^hich the cilia of the rotatory organ act ; so that we cannot explain the 

 W' hole phenomenon otherwise than that the water with the particles contained 

 in it, streaming with some rapidity into the mass w^ith which the body is 

 filled, cannot mix with the latter immediately, but only when its rapidity of 

 motion is diminished by friction, — -just as we see a rapid stream which falls 

 into a sluggish or stagnant pool, or into the sea, still retaining its independ- 



