532 



GENERAL PHYSIOLOGY 



therefore, be supposed that the radiation that forms about the 

 centrosome likewise has its origin in the traction existing between 

 the centrosome and the foamy protoplasm, and that this traction 

 is derived from the chemical relations and diffusion-processes that 

 develop between the two cell-constituents, But only a systematic 

 and comparative investigation of these processes will be able to 

 make this supposition a certainty. The mechanical theories of 

 cell- and nuclear division, which M. Heidenhain ('94/95/96), 

 Driiner (' 94), Rhumbler (' 96, ' 97), and others have very recently 

 put forward, are so contradictory, incomplete and full of hypotheses, 

 that at present it is quite impossible to say anything certain, 

 except of the most general nature, concerning the mechanics of 





FIG. 262. Photographic reproduction of radiating figures. /, Nuclear radiation from a cephalopod 

 embryo. II, Eadiation about two air-bubbles in a gelatine foam which was coagulated by 

 means of chromic acid. (After photographs by Butschli.) 



these complex events. Before all else, as R. Fick (' 97) very cor- 

 rectly emphasises, their molecular-physical relations must be given 

 much more careful attention ; thus far Rhumbler alone has done 

 this properly and to a considerable extent. Further, it will be of 

 essential importance in such an investigation to start from the 

 simplest forms of nuclear division, i.e., from the so-called direct 

 nuclear division, in which there are no complicated figures. The 

 lengthening and simple constriction of the nucleus giving rise to 

 two nuclei is a simple mode of increase of the nuclear surface, the 

 mass remaining the same ; and the subsequent constriction of the 

 protoplasm has the same significance for the cell-body. It is the 

 simplest form of a correction of the disproportion arising between 



