246 J- tibbs 



the muscle cell itself where it possibly exerts some intracellular con- 

 trol on ionic movements and thus the contraction of the myofibrils 

 (Barrnett and Palade, 1959). 



Sperm cells and protozoa in general are not, of course, innervated 

 in the conventional sense and yet these organisms can show a very 

 fine degree of control over their motility. In addition to enquiring 

 into the actual mechanism of movement in these single cells, there- 

 fore, it is also pertinent to ask how this movement is controlled. 



Other authors have made observations relevant to this problem. 

 Thus, Seaman and Houlihan (1951) found acetylcholinesterase as a 

 constituent enzyme of the ciliate Tetrahymena and identified the en- 

 zyme as associated with the pellicular fraction obtained from a cell 

 homogenate (Seaman, 1951). In a brief note, Mann and Legge (Mann, 

 1954) mention the detection of the same enzyme in the tails of ram 

 sperm but not in the heads. While Seaman (1955) suggests that the 

 enzyme activity results from the presence of what he calls "subpellicu- 

 lar neurofibrils" the finding by Mann and Legge of acetylcholinester- 

 ase in organs which have a similar basic structure to that of cilia sug- 

 gests Seaman's pellicular fragments may still have had cilia attached 

 to them. On the other hand, while an acetylcholine mechanism might 

 be located exclusively in the cell body of systems carrying simple cilia 

 with only the basic pattern of two inner and nine outer fibrils, such a 

 mechanism could well extend down or be located in the more com- 

 plex tails of mammalian sperm. Attempts have been made at Leeds 

 (Tibbs, 1960), first of all to confirm the presence of the enzyme in pro- 

 tozoa and then to decide whether or not the enzyme is associated with 

 those basic structures of the cilium and flagellum which are common 

 to all organs of this type. 



No acetylcholinesterase could be detected in homogenates of the 

 algae Polytoma uvella or Poly tomella. caeca. Precautions were taken to 

 guard against enzyme inactivation and the presence of natural inhibi- 

 tors, but homogenates of Tetrahymena pyriformis also proved to be 

 inactive or, at least, to have an activity less than that which would 

 split 0.01 fig of substrate /hr/mg at 37°. In this respect the author's re- 

 sults are at variance with those of Seaman and Houlihan (1951), but 

 are in agreement with the results of yet another worker, Reith (1953), 

 who has also been unable to demonstrate the presence of the enzyme in 

 Tetrahymena. 



With fish sperm (from Salmo trutta and Perca fluviatilis) the situa- 



