18 MORPHOGENESIS IN CILIATES 



term field implies a region throughout which some agency 

 is at work in a coordinated way, resulting in the establish- 

 ment of an equilibrium within the area of the field." "A 

 field," says Waddington, ^^is a system of order such that the 

 position taken up by unstable entities in one portion of the 

 system bears a definite relation to the position taken up 

 by the unstable entities in other portions." 



The region between the rows 7 and 1 corresponds to such 

 a field. The kinetosomes behave differently according to 

 their position. Their maintenance, or their growth and 

 division, depend evidently on the properties of the under- 

 lying cytoplasm. 



The simplest hypothesis, for the time being, is that kinet- 

 osomes must get some specific food in order to grow and 

 divide, and that the specific food must be unequally dis- 

 tributed in the region between the rows 7 and 1. In terms 

 of molecular ecology one should question also the possible 

 role of some specific cytoplasmic particles which could be 

 directly or indirectly responsible for the nursing of kineto- 

 somes. 



