272 THE AMERICAN NATURALIST [Vol.L 



and those having opposite properties in the other, so that 

 the two daughter-cells would then differ entirely in their 

 properties. 



I can but refer briefly here in passing to the interesting 

 theory put forward by Biitschli, to the effect that sexual 

 phenomena owe their first origin to differences between 

 cellular organisms resulting from the imperfections of 

 the primitive methods of cell-division. If we assume, for 

 instance, as so many have done, that one of the earliest 

 qualitative differences between different chromatin-gran- 

 ules was that while some influenced more especially the 

 trophic activities of the cell, others were concerned spe- 

 cially with kinetic functions ; then it might easily happen, 

 after nuclear division by chromidial fragmentation, that 

 all, or the majority of, the kinetic elements pass into one 

 of the two daughter-cells, while its twin-sister obtains an 

 undue preponderance of trophic chromatin. As a conse- 

 quence, some cells would show strong kinetic but feeble 

 trophic energies and others the opposite condition, and in 

 either case the viability of the cells would be considerably 

 impaired, perhaps inhibited. If it be further assumed 

 that cells of opposite tendencies, kinetic and trophic, at- 

 tract one another, it is easy to see that the union and 

 fusion of two such cells, the one unduly kinetic (male) in 

 character, the other with a corresponding trophic (fe- 

 male) bias, would restore equilibrium and produce a 

 normal cell with kinetic and trophic functions equally 

 balanced. On this view, sexual union, at its first appear- 

 ance, was a natural remedy for the disadvantages arising 

 from imperfect methods of nuclear division. 



It is not surprising, therefore, to find that the process 

 of nuclear division undergoes a progressive elaboration 

 of mechanism which has the result of ensuring that the 

 twin sister-granules of chromatin produced by division 

 of a single granule shall be distributed between the two 

 daughter-cells, so that for every chromatin-grain obtained 

 by one daughter-cell an exact counterpart is obtained by 

 the other; in other words, of ensuring an exact qualita- 



