PHYTOFLAGELLATES 131 



an insertion has not been seen by either light or electron micro- 

 scopy is not surprising, considering the difficulty of tracing them 

 at all. The important point is that, by all accounts, the movements 

 of the rodorgan must be caused by something more precise than 

 generalized protoplasmic contraction, and that in the structured 

 sheets we perhaps have an intracellular muscle with a very 

 specific action. 



The leading flagellum of Peranema is assumed to be sensitive 

 at least to mechanical stimuli (Lowndes, 1944; Chen, 1950a), and 

 indeed it is difficult to escape this conclusion when studying the 

 living organism. The second flagellum normally adheres to the 

 body surface and does not participate visibly in swimming 

 movements. 



The Peranema flagellum, with its two ribbons of banded material 

 and its coating of mastigonemes, was described above. In 

 addition to these structures, Roth found a cylindrical rod of 

 homogeneous material enclosed within the flagellar membrane. 

 Near the bases of both flagella, the diameter of this paraflagellar 

 rod exceeds that of the fibrous axis ; cross-sections cut at this level 

 resemble somewhat the flagellum of Eug/ena cut through its 

 paraflagellar body. In Peranema, the rod extends through an 

 unknown length of the leading flagellum outside the reservoir ; it 

 becomes flattened against the side of the trailing flagellum that is 

 adherent to the body. The rods of both flagella may perhaps 

 continue into the cytoplasm. A cross-section through the kineto- 

 somes shows two additional ring-shaped profiles, somewhat 

 smaller in diameter than the kinetosomes but like them composed 

 of nine fibrils; Roth considers these to be the roots of the 

 paraflagellar rods. 



Many euglenoids show a type of body contortion confusingly 

 known as metaboly. This generally appears to be a sort of 

 ameboid movement restricted by the plastic but not notably 

 elastic pellicle. The rather vigorous body movements of Peranema 

 may perhaps involve something more than this. Roth believes 

 that they do, and describes some structures associated with the 

 pellicle that might be contractile. Like the surface oiEuglena, that 

 of Peranema is composed of at least two membranes, separated by 

 a space 3 to 4 m/x wide. A third layer, identified as a membrane, 

 occupies the same position as the vesicular layer in Buglena. 



