264 DAVID W. BISHOP 



it is more closely associated with the loss of a coordinating system, not 

 necessarily involving overt wave propagation, since one can demon- 

 strate that three-dimensional tail movements and cell rotation can 

 occur in the absence of wave propagation in, for example, live sperm 

 of the squid when exposed to less than favorable conditions (Bishop, 

 1958c), a point raised by Lord Rothschild during this conference. 

 Propagation of the wave may not be essential for flagellar activity in 

 more than one plane; propagation certainly is required, however, to 

 effect forward progressive movement of the cell. 



Induced flagellation in sperm models is most simply to be regarded 

 as the result of priming a self-sustaining oscillating system, a view 

 consonant with that expressed by others in this symposium (cf. Pau- 

 tard, Brokaw). It is tempting to compare the mechanism of flagellar 

 activity with that of any one of several unique systems of transiently 

 oscillating muscle preparations (Goodall, 1956; Lorand and Moos, 

 1956; Pringle, 1957), but such comparisons at this time seem based 

 on rather fragile evidence. If a common denominator of cellular 

 movement can be found here, all well and good; on the other hand, it 

 is not inappropriate to recall the work of Kuhn et al. (1959), which 

 demonstrated that all that contracts need not be muscle. 



The characteristics of the response of sperm models to nucleotide 

 has provided compelling evidence that (1) the energy transfer which 

 permits chemomechanical coupling is locally distributed along the 

 flagellum, and (2) wave formation is a local or segmental affair and 

 is not brought about by a whiplash mechanism restricted to the base 

 of the tail. This applies to the extracted cells, and we regard it as 

 equally cogent in the flagellation mechanism of living spermatozoa. 



Regardless of which components within the flagellum prove to be 

 the motile elements — be they the longitudinal filaments or some 

 other, as yet unrecognized, units — it is difficult to conceive of a 

 mechanism which does not demand simultaneous "shortening" and 

 "elongation" at any given section of the tail. Even the highly spec- 

 ulative suggestion of a sliding-filament theory for sperm movement 

 (Afzelius, 1959) would require overlapping on one side and stringing 

 out on the other. Contraction, if in the literal sense it does occur, 

 must then accompany relaxation; likewise, as any one motile element 

 passes from the contractile to the relaxing phase, its counterpart must 



