464 THE 4 MERic n \ \ nii\ij^r [Voi lv 



action ot 111 (pi^tiiic 01 mliihitino faolor / Tlius the constitu 

 tion of tlio Snowflake snides »i\'iMg: rare slender progeny may 

 be IS'D/ts'd or Bb'1/ds'i. A serious theoretical difficulty seemed 

 to arise m the apparent necessity^ for several sp(H'ihe "in- 

 hibitors' all sriviiiii^ the same •'normal" tvpe, and also for rela- 

 tively frequent dominant mutations. Perhaps, however, the 

 api)arent mutation may usually consist m the development or 

 disappefirance ot some condition of duplication in one chromo- 

 some oL the [)air concerned. (.)i-io:m ot apparent mutants 

 throucrh. duplication of whole chromosoinies, as seems to have 

 been demonstrated for a remarkablv similar series of mutant 

 foims m Datum (Biake^lee, Belluif? and Farnham, 1020), s(cm> 

 to be precluded in these cases bv the evident linkage phenomena. 



Howard B. Frost 



THE XP]rROMOTOR APPARATUS OF PARAMECIUM 



