196 THE BIOLOGY OF STENTOR 



fibers connecting the cilia in Stentor are always to the right of the 

 ciliary meridian so that one cannot turn a kinety upside down and 

 have the over-all pattern remain the same. Endomyonemes or 

 M-bands also show graded differences in tapering widths and in 

 density of lateral connections. Polarity may even characterize the 

 granular stripes, for in pigmented forms grafted in heteropolar 

 orientation there is always a white line or space where granules 

 are not continuous at the place of abutment. Since we do not 

 conceive of a polarity in these granules themselves, it follows that 

 the ectoplasm in which they reside may itself be polarized, though 

 little differentiated otherwise. 



Balbiani (1893) recognized that original polarities were retained 

 in Stentor fragments as shown by the direction of their swimming; 

 and Prowazek (1904) made the same claim on the basis that folded 

 longitudinal halves eventually draw themselves out in correspon- 

 dence with the original polar axis. Causin (1931) found that 

 triangular fragments cut from the middle of the cell retained their 

 polarity although the " bulk axis " was at first at right angles to 

 this, but Weisz (1951b) provided a more convincing demonstration. 

 He cut stentors in such a way that the future site of the primordium 

 was bent around over the anterior end of the cell, or conversely, 

 part of the general striping was bent around so that its forward end 

 pointed backward toward a much-shortened primordium site. 

 When anlagen appeared they followed the striping, as did the 

 general reconstruction of shape, in complete disregard of the 

 " bulk axis ". It is in fact difficult to conceive how a fluid endo- 

 plasm could have an axis at all. The main point is that intrinsic 

 polarity persists in the striped ectoplasm, no matter how oriented. 

 Weisz's inference, that the polarity of the so-called stomatogenic 

 kinety determines the polarity of the oral primordium and that of 

 the entire cell cannot be the case, however, because the primordium 

 first appears at nearly right angles to the striping and at a consider- 

 able distance from the kinety in question, and because reversing 

 the whole sector containing the primordium site does not result 

 in reversing the polarity of the entire cell. 



For intrinsic polarity within the ectoplasm is best demonstrated 

 by altering the orientation of parts of the cell or separating parts 

 and turning them around. The simplest response is that the 

 disarranged parts shift into homopolar alignment. If a patch is 



