52 THE BIOLOGY OF STENTOR 



incision because of them. Klein (1932) may have demonstrated 

 such transverse fibers in his silver staining of a cortical network 

 in S. tgneus; but the EM studies of other species have revealed 

 no specialized connections between adjacent rows. Another impor- 

 tant difference is that the system in Stentor is refractive to silver- 

 staining and neither the wet (Villeneuve-Brachon, 1940) nor the 

 dry (Weisz, 1949a) method gives the beautiful network demon- 

 strable by this means in most other ciliates. 



If the ribbon bundles we are now discussing were indeed what 

 earlier workers described as the myonemes, as appears from 

 correspondence in location, certain of their remarks may still be 

 pertinent. Popoff (1909) stated that the bands were not only more 

 numerous but correspondingly wider in larger stentors, 57 of 

 which were studied in this connection. Anteriorly, Schroder (1907) 

 found fine extensions of their much-tapered ends leaving the 

 cortex and passing inward and forward to attach to the outer 

 margin of the membranellar band. Dierks (1926a) seems to have 

 seen something like this too. Johnson (1893) noted that the bands 

 are straight during contraction but much convoluted at the 

 moment of beginning extension before the lengthening of the cell 

 has again stretched them straight (Fig. iob). This observation 

 was confirmed by Faure-Fremiet et al. as the behavior of the 

 ribbon band. Gelei (1926) reported that the bands in the clear 

 stripes of the frontal field are not tapering but of uniform thick- 

 ness. In the expanded field he found the bands to be still slightly 

 sinuous and in the contracted field they were strongly coiled. In 

 this area the bands therefore did not seem to become straight 

 when contraction occurs, yet he still regarded their function else- 

 where as contractile. 



A nice point was made by Gelei when he remarked that if the 

 fibers responsible for sharp contraction were fastened only at their 

 anterior and posterior ends they would, on developing a tension, 

 pull to the center of the cell and not form an arc following the 

 contour of the surface as is in fact observed. Contraction would 

 then draw the cell into the shape of a much-flattened sphere. 

 (Incidentally this very shape, with corresponding retraction of 

 the frontal disc, actually occurs in introversus, in which the 

 disposition of the contractile fibers may therefore be quite diflFerent 

 from that in all other known species of Stentor.) Therefore Gelei 



