86 MORPHOGENESIS IN CILIATES 



'^Once a certain degree of complexity is introduced into a 

 medium, the complexity will increase under its own mo- 

 mentum, physically, chemically, or both." 



^'Given just the number of asymmetrical conditions in 

 the environment, the chemical complexity of protoplasm is 

 sufficient to evoke further spatial patterning. This, in turn, 

 increases the complexity of the gradients and phases and 

 so evokes a still more complex patterning, the whole cycle 

 repeating itself until the system has reached a condition of 

 dynamic stability or of rigidity as in fructification. But 

 development is a- perfectly orderly phenomenon; therefore, 

 segregation of particles must be controlled by severe and 

 unescapable laws. This is perhaps the reason for the suc- 

 cess of the cortical theories postulating an organization of 

 the cortex." 



I should like to say that an orderly or organized asym- 

 metry, like that of an egg or of a ciliate, may only be the 

 reflection of cortical properties. A constantly flowing or 

 potentially flowing endoplasm cannot be asymmetrical. 

 The building blocks of the different organelles may be asym- 

 metrical; the organelles may be asymmetrical. But if we 

 consider the ciliate as an organism, we reach the conclusion 

 that organized asymmetry or simply organization can be- 

 long only to a more or less rigid, or more or less permanent, 

 system, that is to say, to the cortex. 



It is known that the dextral or sinistral torsion of Lim- 

 naea is controlled by a pair of allelomorphic genes. But 

 the type of structure is determined not by the genetic con- 

 stitution of the organism, but by that of the oocyte from 

 which it arose. The direction of torsion depends on some 

 structure which is formed during the growth of the oocyte. 

 The hypothesis that this structure is cortical seems likely 

 and is in agreement with A. L. Cohen's statement (1942) 

 that "a surface is not a mathematical plane but a layer of 

 more or less oriented molecules or atoms with fields of 

 forces which in some instances may be quite powerful." 



