FINE STRUCTURE 53 



postulated that the contractile bands were attached at successive 

 points to the " epimuscular band ", by which I think he meant the 

 pelHcular clear stripe. The ectomyonemes or km bands fulfill this 

 requirement in their connection with the pelHcle. And this con- 

 nection not only allows the bands to draw the whole cell into a 

 compact sphere rather than merely pulling the head and foot 

 together, but also makes possible the continued contraction of 

 isolated fragments because the bands need no end anchors. It 

 might even make possible the independent contraction of different 

 sections of the band, thus accounting for Dierks observation that 

 in simple contraction the anterior part of the band shortens while 

 the posterior part remains unthickened and thrown into curves, 

 itself straightening and thickening if super-contraction follows. 

 If indeed contractile, the ribbon bundles as muscles should have 

 their antagonists (Ishikawa, 1912), which would be whatever is 

 responsible for drawing out the cell. Elasticity of the pellicle may 

 be one factor here and the accessory bands shortly to be mentioned 

 another, but this matter is quite uncertain. 



Lying interior to the ribbon bundles, Faure-Fremiet et al. made 

 out a layer of trabecular cytoplasm which in the study of Randall 

 and Jackson seemed to be another set of bands under the clear 

 stripes, tapered forward, wider posteriorly, and having transverse 

 connectives (Fig. iga). In their composition, these bands and 

 their connectives showed only short fibrils more or less randomly 

 arranged but tending to align with the axis and not orderly 

 stacking of long fibers. This is the type of structure Faure-Fremiet 

 and his associates find in the '^endomyonemes" of stalked ciliates 

 like Vorticella. Therefore these bands may be contractile. Accor- 

 dingly, Randall and Jackson referred to them as "M bands". 

 The transverse connections may be what Prowazek (19 13) observed 

 in vivo: delicate transverse connections between the substance of 

 the clear stripes in the expanded ectoplasm of stentors ''exploding" 

 or deliquescing on the surface film. Randall and Jackson found 

 that these transverse connections between the M bands w^ere 

 prominent posteriorly but fewer at the forward end of the animal. 

 Their demonstration that the matrix of the bands is continuous 

 with that of the connectives would seem to imply that action of the 

 latter could not be independent, say, in causing extension of the 

 animal. 



