168 GENERAL HISTOEY OF THE INTUSORIA. 



and this is not only made evident by the multifold changes of form which they 

 undergo in the course of vegetation, and by the filiform prolongations and 

 ramifications which are produced directly from their substance, but is clearly 

 shown by the transformations which the primordial cells pass through in con- 

 sequence of external influences. Under certain circumstances, namely, the 

 filiform processes may be retracted, being torn away from the envelope-cell 

 and taken up into the substance of the primordial cells ; the produced ends 

 of the primordial cells also disappear, the latter becoming rounded off into 

 their original spherical or short -cylindrical form. Such a change would be 

 impossible if the primordial cells were surrounded by a rigid membrane, such 

 as that of the envehpe-cell for example. Still more rapid and decided are the 

 metamorphoses which the primordial cells undergo in the interior of the 

 envelope -cell, through influences destructive to the life of the organism. 

 These phsenomena, usually called dissolution, do not change the rigid enve- 

 lope-cell at all ; but they totally decompose the primordial cells, depriving 

 them of their form and dissolving them into a single structureless green mass, 

 which lies upon the inside of the envelope-cell, frequently destroying all e^d- 

 dence of the origin from eight spheres, while not a trace of special enveloping 

 membranes comes to light. These phsenomena of dissolution moreover indicate 

 that the envelope-cell, as I have already mentioned, is composed of a delicate 

 memhrane encloshig a clear watery fluid, which cannot be dense, gelatinous, or 

 mucilaginous, since it is readily displaced by the radiating filaments and the 

 dissolved substance, and which therefore is very similar to pure water, if not 

 exactly the same. 



" Motion. — The cilia which are protruded from the equator of the envelope- 

 cell are but short inside this ; but the portion projecting into the water is much 

 longer and vibrates actively, thereby causing all the movements. During 

 therr vibration the cilia are difiicult to detect ; but when dried on glass, and 

 still better by wetting them with iodine, they may readily be traced in their 

 whole length, especially if sulphuric acid is added, this rendering them more 

 distinct and giving them a darker coloiu\ The motion of the entire organism, 

 depending on the eight pairs of cilia, exactly resembles that well known in 

 the Algae and many Infusoria. First there is a rapid revolution round that 

 axis of the envelope-cell wliich passes through its poles and stands perpen- 

 dicular to the ring of primordial cells, so that the envelope-cell rotates like a 

 wheel upon its axle. In the polar view (XIX. 38), our form gives exactly 

 the impression of a revolving wheel, while in the equatorial view (XIX. 39), 

 where the primordial cells are mostly elongated, it has more the aspect of a 

 globe turning upon its axis. Besides this revolution on its axis, which endui'es 

 throughout the whole life, there is an advancing movement, which produces 

 a very irregular course ; in this way these organisms screw themselves, as it 

 were, onwards in the water. Sometimes they swim straight out with uniform 

 rapidity, the pole going first, the rotating ring of primordial cells standing at 

 right angles to the coui'se and appearing only in one line ; sometimes they 

 turn round, so that the equatorial plane presents itself as a circle again (in 

 the polar view) : they rotate thus round their centre without moving from 

 the spot ; then they set one pole forward and swim on in another dii-ection, 

 bend to the light or to the left, or turn quite round, mostly -wdthout any per- 

 ceptible obstniction, move in curves of the most vaiied kinds, run round any 

 point in spiral lines, come into different planes, sometimes ascending, some- 

 times descending ; in short, they exhibit aU those most complex and wonderful 

 dhsenomena of locomotion which we are acquainted with in the mo\'ing propaga- 

 tive cells of the Algae, — and, as I have demonstrated elsewhere, in exactly the 

 same vjay in the Astomous and Anenterous Infusoria (Monadina, Asiasioia, 



