Evidence from Protozoans 365 



ramifying zone." The list of structures enumerated as aris- 

 ing de novo should be recalled and the further fact recog- 

 nized that like this first sign of fission, they all pertain to 

 the superficial part of the animal's body. "The gradual 

 evolution," we previously quoted Johnson as saying, "of 

 structures so complicated as membranellae, from a mass 

 of indifferent protoplasm, is very striking." 



What of the nucleus while those parts 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 mcganucleus 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 disapj>earance of the commissures, 

 the nodes becoming appressed." l The various positions 

 and conditions of the nucleus here referred to are shown, 

 iiHjn, 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, arc indi- 

 cated in the figures. Johnson speaks of the great activity 

 of the nucleus in some of its stages showing something ap- 

 proaching an amoeboid character; but there is no intimation 

 either by position or by activities that the nuclear changes 

 are correlated in any detail with the formation and growth 

 of new organs of the bodv. 



But, it will be said, prevalent views about the macronu- 

 cleus would not lead one to expect it to participate in the 

 development of organs. The micronuclei of the group of 

 organisms to which S ten-tor belongs, being chiefly concerned 

 in reproduction) would be presumed to contain the hereditary 

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

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



