292 DAVID W. BISHOP 



acteristic of flagellar mechanisms, as distinct from a system of con- 

 tractile proteins typical of muscle, remains to be seen. If the existence 

 and operation of such a single macromolecular entity is established, 

 it would favor the concept of a monocomponent rather than a bi- 

 component system of contractile elements in sperm. 



How the contractile elements are built into the longitudinal fila- 

 ments, if indeed they are, is currently an open question. Pautard 

 suggests that they may be relatively short segments, not necessarily 

 extending the length of the fibril, an idea also raised earlier by Gray. 

 This problem might be further explored, along the lines suggested 

 by Sir James and Lord Rothschild, by isolation of the fibrils in a 

 functional state. The relative ease with which fish and fowl sperm, 

 for example, can be longitudinally dissociated should not make this 

 technically unfeasible. 



Many other unresolved problems confront us. A basic question, 

 one upon which the opinion of the symposium participants is split 

 right down the middle, concerns the nature of the normal wave pat- 

 tern, whether planar or helical. Some discrepancies may be attrib- 

 uted perhaps to species differences and others to methods of observa- 

 tions and recording of movement. Possibly what is needed is the 

 construction of a wide-angle binocular microscopic device which can 

 simultaneously view the same sperm at an angle of some 90 degrees, 

 although even here one can expect some variation in interpretation 

 of the actual waveform. 



The tantalizing question of why 9 + 2 fibrils as a universal pat- 

 tern in flagella and cilia has arisen on numerous occasions and has 

 been discussed with sound judgment by Rothschild. His point that 

 the number 9 may be more closely associated with the intrinsic prop- 

 erties of centrioles of the division apparatus than with the require- 

 ments of the axial filaments which arise from a modified centriole 

 is consonant with the observations of de Harven and Bernhard (1956) 

 on the centrioles of a variety of vertebrate cells. The question would 

 seem to be open to further attack by developmental studies of the 

 axial bundle: its origin in the spermatid centirolar derivative and its 

 differentiation in a sperm like that of Polyphemus, a crustacean, in 

 which an amoeboid cell is claimed to transform, under experimental 

 conditions, into a ciliated gamete (Geddes and Thomson, 1890). 



