EXTENSIONS 369 



kinetosomal orientation, some pattern factor in addition. 



Specifically in reference to his studies on Stentor (Weisz, 1951c, 

 1954) developed a theory of morphogenesis in ciliates involving 

 three postulates : first, that self- reproducing kinetosomes represent 

 a hierarchy, with oral granules dominant over those of a stomato- 

 genic kinety or primordium site and these in turn dominant over 

 those of other kinetics of the more generalized lateral body surface ; 

 second, that this hierarchy represents the degree of ascendency in 

 competition of the kinetosomes for their "food" or the special 

 metabolites supplied by the endoplasm from biochemical activities 

 supported by the macronucleus which they require both to grow 

 and to maintain themselves; and third, that the kinetosomes in 

 turn act back, enzymatically, on the part of the macronucleus 

 nearest them. How this system was thought to operate may be 

 illustrated by the case of regeneration. When the feeding organelles 

 are excised, the upper level of the kinetosomal hierarchy is vacated 

 so that the metabolites can flow to the kinetosomes of the next 

 level — those of the stomatogenic kinety or, if this was also 

 removed, then the next adjacent body kinety — which are then 

 able to multiply and produce oral cilia for the anlage of a new set 

 of feeding organelles. Once formed, this new set again exhausts the 

 special metabolites for oral cilia so that further primordium 

 formation is inhibited. (In division and reorganization, the oral 

 kinetosomes somehow lose their competitive ascendancy so that 

 the kinetosomes of the stomatogenic kinety are no longer held in 

 check.) The oral kinetosomes in place now react with adjacent 

 nodes of the nucleus, maintaining their capacity to produce the 

 special metabolites, while those far distant lose their capability, 

 and morphostasis is hence stabilized. 



The effectiveness of this hypothesis depends upon two points : 

 first, that the postulated metabolites are necessary for the main- 

 tenance of existing feeding organelles, and second, that these 

 metabolites are present only in limited quantity. Only on the basis 

 of these assumptions would there occur that competition which 

 would explain the integration of the organism, e.g., that it never 

 has more than one set of feeding organelles. Yet I do not think 

 that either of these points have been substantiated by subsequent 

 studies. The formed feeding organelles and body cilia of enucleates 

 are often maintained to the point of death or at least they continue 



