MACRONUCLEI 51 



When the macronucleus undergoes an unequal division as in 

 amitosis, we may therefore suppose that it suffers an irreversible 

 change, as does the nucleus of Ascaris undergoing chromosome 

 diminution (q.v.). And such a change cannot be undergone by a 

 nucleus retaining the full genetic potentialities of the species {cf. 

 Ch. VIII). 



Summing up, recent work leaves no doubt that : whenever a 

 nucleus divides to produce two daughter-nuclei physiologically or 

 morphologically equivalent to it, i"t does so by mitosis. Further, 

 the effective test of a nucleus is not primarily in its chemical or 

 physical properties, but in its behaviour : a nucleus is a cell-body 

 which arises or reproduces by mitosis. 



