222 



THE EVOLUTION OF SEX. 



process, in which the nucleus plays an important and probably 

 a controlling part. By a complicated series of changes, both 

 in form and position, the essential nuclear elements group 

 themselves so as to form the daughter-nuclei of each product 



Illustrating thelNIechanisin of Cell-Division, — (a) the 

 chromatin or essential elements of the nucleus 

 forming an "ecjuatorial plate " in the one figure, 

 drawn towards the poles to form two daughter- 

 nuclei in the other ; (/') the almost '" muscular " 

 threads ; (c) the protoplasmic centre from which 

 these radiate. — From Boveri. 



of division. The orderliness and complexity of these changes 

 forbid any off-hand attempt to analyse the real physiological 

 movement by which the growth of all multicellular organisms 

 is effected. That attractions and repulsions do exist within the 



