No. 638] TYPKS OF MUTATIO.X.^ 259 



already meiitloiiod in that there are 4 lioiiH.lounuv .-ln-o- 

 mosomes in each set in somatic cells. Tlic iKiiimlduous 

 chromosomes therefore form tetrasoincs. id use .i n. w 

 term,^ instead of disomes as in normals oi- in-oiiics ;i> m 

 triploid plants. Members of these let i-a-oiiic- ;i]>ii;ii-- 

 ently assort at random iii th(^ reduction (li\isi(.)i. In 

 consequence, certain ix'cnli.-ii-itics m Invidiiiu lifli.-iNior 

 result. Plants duplex tnr n (l.niiinaiit factor lAAaa) 

 will ^^hen ^elfed, uin. a laln. ot doiniiiaiit^ tn I 

 ce-ix," ill the nlt.pnnu Plants ^.niph \ tm tin .Imni- 

 nant (Anna) will -ivr a ;! : 1 ratio in their ottsi)nnu-: hut 



in the ne\t i;enei <it ion. i^'ant^ tiiplex toi tin doninumt 

 (AAAa) will give in the immediate otTsi)rin- all domi- 

 nants; one quarter ol which, however, niav he ex])ected 

 to give a 35:1 ratio m a later licnerat ion. 'riie i-esidts 



expected fr(nn selliim- the 5 zvu'otic are shown in 



Table III. 



It miglit 1..- expeote.l that mutant forms woul.l he 

 fomid in which douhlmu- ol the cliromosoiiial immher had 



would bear the same relation to tetraploid |)Laiit> with 

 all the sets involved that the I*oiii<ettia tv])e ..f mutants 

 bear to trijdoid plants. Thev hav m.t vet been found, 



