Evidence front Protur:oans 365 



ramifying zone." The list of structures ciiuiiu rated as aris- 

 ing de novo should be recalled and the tiirtlic r tact rrcocr- 

 nized that like this first sign of fission, tiiev all pntaiu to 

 the superficial })art of the aiiiinars body. "Tlie gradual 

 evolution," we ])reviously (juoted Johnson as saying, "of 

 structures so complicated as nicnihranellai-, fiom a mass 

 of indifferent protoplasm, is wry striking." 



What of the nucleus while these |)arts are being started in 

 the indifferent protoplasm? Considering the time at which 

 Johnson did this piece of work, his account of the behavior 

 of the macronucleus during fission is very full. ''At the be- 

 ginning of fission," he says, "the megaiuicleus has its usual 

 spiral disposition in the body. The first alteration, just 

 previous to the appearance of the new pharynx, is a straight- 

 ening of the nucleus and disappearance of the commissures, 

 the nodes becoming appressed." ^ The various positions 

 and conditions of the nucleus here referred to are shown, 

 mgn, of the figures. 



The complete obliteration of the nodulation typical of the 

 resting nucleus, the great elongation of the nucleus and its 

 gradual reformation at each end, and the final division after 

 the preparation for body-fission is far advanced, an- indi- 

 cated in the figures. Johnson speaks of the great activity 

 of the nucleus in some of its stages showing something aj) 

 proaching an amoeboid character; but tlu-re is no intimation 

 either by position or by activities that the miclear c-hanges 

 are correlated in any detail with the format icju and growth 

 of new organs of the body. 



But, it will be said, prevalent views about the niacronu 

 cleus would not lead one to ex))ect it to particijjate in tlu- 

 development of organs. The micromiclei of the grouj) of 

 organisms to which Stcntor belongs, being chiefly concerned 

 in reproduction, would be presumed to contain th( hereditary 

 substance, and so to them and not to the macronucleus ought 

 inquiry to be directed for evitlence, if such there be, of 



