No. 3-J MORPHOLOGY OF THE STENTORS. 483 



are multiplied in the new adoral zone at time of fission, i.e., by 

 the intercalation of a new clear stripe. 



Myonemes . — Standing in close relation to the stripes are 

 the contractile elements, called by BUtschli 7nyottemes. One 

 of these underlies each clear stripe, and thus subtends a row of 

 cilia (Figs. 5, 7, 9, 12). In the living Stentor the myonemes 

 are hyaline, flexible, and exceedingly contractile fibrils ; in a 

 Stentor killed with osmic acid or corrosive sublimate, they 

 become rigid, highly-refractive rods (Fig. 11). Butschli ('89, 

 p. 1298) describes the myonemes of 5. ccejiileus as being oval 

 in transverse optical section ; to me, however, the section has 

 always appeared to have a circular outline (Fig. 5). Neither 

 have I been able to make out the transverse striations figured 

 by Butschli, even with the 2 mm. apochromatic homogeneous 

 immersion of Zeiss. While I do not assert the absence of the 

 striae, owing to my inability to see them, I would nevertheless 

 suggest that the appearance observed by Butschli was of 

 artificial origin. 



Myonemes attain their largest size in S. asmleus, where 

 they are plainly visible in the living animal, if it be sufficiently 

 compressed and examined with a power of 500 diameters. 

 In other highly contractile Stentors, as S. polymorpJms 

 and S. roeselii, the myonemes are very distinct after 

 application of reagents. In 5. pyriformis, on the contrary, 

 where the contractile power is much less, the myonemes are 

 exceeding minute (Fig. 9, nm^. 



The myonemes are to be regarded as highly-specialized 

 differentiations of the ectoplasm, endowed with a contractile 

 power not less than that of striped muscle. In both cases, 

 the highly developed contractility undoubtedly has its origin 

 in the comparatively feeble contractile power of protoplasm. 

 Engelmann's ('75) beautiful researches on the contractile 

 substances of the Protozoa have shown that the general 

 ectoplasm of Stentor is anisotropic, and therefore probably 

 contractile. He assigns to it the slow and gradual contraction 

 one often sees in Stentor, so different from the lightning-like 

 shortening effected by the myonemes. 



It is exceedingly interesting to watch the action of the 



