CHAPTER 4 



Aspects of the Kinetosome 



One kinetosome is always generated by division of an- 

 other. We see kinetosomes dividing and have no evidence 

 whatsoever of their formation de novo. They are endowed 

 with genetic continuity. It is the custom to refer to such 

 particles as "self-reproducing" or ''autocatalytic" units. 

 These terms should not be understood as implying that the 

 particles are independent. A self-reproducing granule is by 

 no means a self-sufficient granule. When we refer to kine- 

 tosomes as self-reproducing units, this means only that the 

 kinetosome never arises de novo, and that some specific 

 structure or template, present in the kinetosome, is neces- 

 sary to organize other molecules into a new kinetosome: 

 like genes, they can only be generated by, or in the presence 

 of, an equivalent structure 



The maintenance of these kinetosomes depends on local 

 conditions. This is clear when we consider the rows x, y, z. 

 These rows, bipolar in the tomont, are reduced in the 

 trophont to short segments with a small number of kineto- 

 somes. One can interpret this in two ways: either the pos- 

 tulated specific substance necessary for the maintenance of 

 the kinetosome is present in limited amounts and disappears 

 in certain regions of the ciliate; or, in these region a new 

 substance, or enzyme, is formed, which dissolves or lyses 

 the kinetosomes. The choice between these two possibilities 

 is difficult. 



Let us remember here one of tne propositions of Paul 



Weiss (1947) concerning molecular ecology: "Survival and 



27 



