54 THE BIOLOGY OF STENTOR 



Extension of stentors to over six times their length when 

 maximally contracted calls for an adequate explanation but is still 

 a mystery. Randall and Jackson's report states that the volume is 

 quadrupled on extension but I think they must have meant the 

 surface area. 



Walls of the M bands as described by the British v^orkers are 

 surprisingly indefinite, becoming confluent v^ith endoplasmic 

 vesicles so that the bands are very intimately related to the endo- 

 plasm, and this could account for the trabecular appearance 

 observed by the French investigators. These bands seemed to 

 have no connection with the pellicle, which of course poses the 

 problem of how they could produce the movement of anything 

 but themselves. One also wonders why stentors should have two 

 parallel contractile bands when one would seem to be sufficient. 

 These and other problems of structure and function we hope will 

 be resolved by further studies in this actively developing field. 

 Apropos of this, Causin's (1931) surprising statement may be 

 repeated : that although a cut into the side of a stentor is followed 

 by prompt healing and does not initiate the formation of a regenera- 

 tion primordium, there results nevertheless a cryptic resorption 

 and replacement of the myonemes. This observation should 

 certainly be checked. 



In addition to understanding the static structure and short-time 

 activities of the cortex, we need to learn how its elements grow and 

 dediflFerentiate, develop and increase in number, as well as how 

 they manage surprising performances in mending and realignment 

 after cutting and other gross disturbances. These capabilities seem 

 contradictory to the fineness and complexity of the structures 

 present and tax the imagination to conceive how they are possible. 



(d) Fiber systems of doubtful status 



Still other types of fibers have been reported in the clear stripes. 

 They were located adjacent to the myonemes and described as 

 unvarying in thickness and convoluted in the contracted animal, 

 therefore presumably nervous in function and not contractile. 

 We have to call them doubtful because these reports did not 

 present at the same time a clear description or, indeed, indicate 

 any awareness of possible kinetodesmata. Neresheimer (1903) 

 seems to have had a bias for completing the roster of '* tissues" 



