THE MITOTIC CYCLE 



ultimate structure of living protoplasm is not exclusively or even mainly 

 fibrous in nature, and that 'models' based on this conception such as 

 those of Seifriz^^ and Frey-Wyssling^^ are misleading. A fresh 

 approach to the problems of cytoplasmic ultrastructure is being made 

 by KoPAC^^ ^' based on observation of the 'Devaux effect', which 

 is the increase in area on denaturation of a protein film absorbed 

 at an oil- water interface. Thus the surface of oil droplets, microinjected 

 into a sea-urchin egg, wrinkles when the egg is cytolysed. 



Although any strictly quantitative investigation of protoplasmic con- 

 sistency and movement must wait on progress in the study of the physics 

 of elastic fluids, yet much could still be done empirically by combining 

 different techniques. For instance, it would be valuable to know how 

 far the physical properties of cytoplasm could be matched by a mixture 

 of cell fractions of varying particle size, and whether mitochondria 

 isolated by the method of Hogeboom and his colleagues show any 

 movement under the influence of electric fields, or in the presence of 

 substrates appropriate to the enzymes which they are known to contain. 



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28 



