Natural History of the Vorticellae. 205 



ing during contraction are most distinctly seen when a 

 colourless or slightly coloured Stentor lies exactly in such 

 a position that one looks upon the circular sucking-disk ; 

 we then see, in a state of repose, all the separate muscles 

 starting from its circumference in a serpentine form ; but 

 at the moment when the animal jerks itself together and 

 therefore shortens itself, the serpentine form disappears 

 entirely, and the muscles become straight. The straight mus- 

 cles immediately begin to relax again, and to fall back into 

 the serpentine form, and the Stentor again elongates itself." 



Lieberkiihn, therefore, interprets the pale strise as sharply 

 contoured muscular fibres, whilst Stein regards them as mere 

 fuiTows formed by the cuticula, which have nothing to do with 

 muscles, and which, under certain states of contraction, only 

 apparently occur as " limpid fibres bounded by double contours," 

 but in reality are portions of the cuticula folded in like a groove. 



The decision of this point, however, seems to me not to be 

 very difficult by careful and unprejudiced examination. If we 

 once more examine our Stentor ccertdeus we see that the two 

 systems of strise are certainly of completely different nature ; 

 the broad streaks consist of a softer mass, more or less darkened 

 by imbedded blue pigment-granules, and the narrow ones of a 

 firmer hyaline mass destitute of granules. 



Now, as regards the substance of the broad streaks, in the 

 first place we see in them, with the exception of the numerous 

 irregularly scattered granules, no trace of special formative 

 elements, or special structural conditions, and especially 

 nowhere any formation of fibres or cells, either in the fresh 

 state or after artificial treatment. What is there to compel us 

 to regard these striee as comparatively highly differentiated 

 muscular substance, even comparable to the transversely striated 

 muscles of the higher animals ? According to Stein, the 

 strongly refractive granules imbedded in the mass are to be 

 considered to represent the enigmatical disdiaclasts of the 

 transversely striated muscles. But with what justice, we must 

 ask, can we regard the granules which occur in almost every 

 thing that is called protoplasm, and indeed almost constitute a 

 characteristic constituent of it, as equivalent to the disdiaclasts 

 of the transversely striated muscular fibres ? Where are the 

 sarcous elements constituted by the disdiaclasts ? Where are 

 the true muscular fibres ? How is the property of double refrac- 

 tion, which is characteristic of the disdiaclasts, demonstrated ? 

 And, lastly, where do we find a distinct longitudinal and trans- 

 verse striation ? Stein remarks that during strong contractions 

 dark transverse lines are produced, by which the stria? acquire 

 a striking resemblance to the transversely striated muscular 



