484 JOHNSON. [Vol. VIII. 



myonemes in a strongly-compressed Stentor as they alternately 

 extend and contract ; and no one who has once observed them 

 under these conditions can doubt that they are responsible for 

 the contractions of the animal. Lieberkiihn ('57) was the first 

 to observe the contraction of the myonemes, and it has since 

 been very accurately and minutely studied by Engelmann ('75). 

 Lieberkiihn thus describes their action : 



" Es sind scharf contourirte kornchenfreie Fasern etwa von 

 der Breite der kornchenfreien Zwischenraume, unterhalb deren 

 sie der Langsaxe des Korpers nach verlaufen ; sie setzen sich 

 vorn unter dem grossen Wimperkreis und hinten am 'Saugnapf ' 

 an ; einige von ihnen vereinigen sich wahrend ihres Verlaufs. 

 Am deutlichsten sieht man die bei der Contraction eintretenden 

 Veranderungen, wenn ein farbloser oder wenig farbiger Stentor 

 gerade so liegt, dass man auf den kreisformigen Saugnapf blickt ; 

 man sieht alsdann von seinem Umfang im Zustand der Ruhe 

 alle einzelnen Muskeln geschlangelt abgehen ; in demselben 

 Moment aber, wo sich das Thier zusammenschnellt, also ver- 

 kiirzt, verschwindet die geschlangelte Form vollstandig, die 

 Muskeln strecken sich gerade." 



As Lieberkiihn states, the myonemes extend from the 

 adoral zone to the "sucking-disc," or foot. When in the con- 

 tracted state they are much thicker posteriorly than anteriorly 

 (Fig. 11), probably because the most contraction takes place in 

 the former portion. They always remain very indistinct towards 

 the adoral zone, and although I have been able to trace them 

 up to it, I have not seen the manner of their ending there. 

 At the other extremity, however, the termination of the 

 myonemes is evident enough (Fig. 12). They end abruptly 

 just at the edge of the pellicula bordering the naked proto- 

 plasm of the foot. 



In the ramifying zone not only the clear stripes branch, but 

 also the myonemes underlying them, as I have sketched in 

 Fig. 10. The myonemes are represented in the extended con- 

 dition, and are therefore thrown into folds. The presence of 

 these convolutions in the myonemes, entirely independent of 

 any corresponding folds in the ectoplasm, indicate that there 

 is no firm connection between the two. The convolutions are 



