170 



THE AMEBIC AN NATURALIST [Vol. XLIS 



cell was homogeneous, but that it differed slightly in dif- 

 ferent germ cells of the same species as a result of ex- 

 posure to slightly different conditions during its past 

 history. What would be likely to happen when two dif- 

 ferent samples of chromatin came together in the zygote? 

 The result would surely depend upon the interaction of 

 the complex colloidal multimolecules of which the chro- 

 atin is composed. Various possibilities would arise. 

 (1) The two samples might differ in such a way as to 

 act as poisons to one another, disturbing each other's 

 molecular equilibrium to such an extent that neither 

 could survive. This is possibly what happens when an 

 ovum is fertilized by a spermatozoon of a distinct 

 species, though there are, of course, exceptions. (2) 

 They might be so alike as to be able to amalgamate 

 more or less completely, so that there would simply be 

 an increase of chromatin of possibly more or less modi- 

 fied constitution. (3) They might continue to exist side 

 by side, each maintaining its own individual character. 



In the third case the union of the two different samples 

 would give rise to a mass of chromatin of twofold na- 

 ture, and repetition of the process from generation to 

 generation would, as Weismann has shown, result in 

 ever-increasing heterogeneity, until the chromatin came 

 to consist of a great number of different concrete par- 

 ticles, each of which might conceivably differ from all 

 the others. But when two heterogeneous masses of 

 chromatin meet in the zygote there may be all sorts of 

 mutual attractions and repulsions between the different 

 colloidal multimolecules, for all three of our supposed 

 cases may arise simultaneously, and thus the results may 

 become extremely complicated. 



The chromatin of the germ-cells in all existing or- 

 ganisms is undoubtedly heterogeneous, and this hetero- 

 geneity may be to some extent visibly expressed in its 

 arrangement in more or less multiform chromosomes 

 during mitosis. We may provisionally accept Weis- 

 mann 's view that these chromosomes are themselves 



