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THE AMERICAN NATURALIST [Vol. LV 



Let us, then, take the coiii'se which is obviously- more useful, 

 and also honor tlir nicnioiy of tlie grreat pioneer of genetics, by 

 applying his name t<» his great idea in all its later ramifications. 

 But — wherever newer and more precise terms will better pro- 

 mote the science of genetics, let us be ready to use them. Shull's 

 recent contribution to genetic terminology promises considerable 

 and lasting usefulness. 



TTowAKD B. Frost 



Ix connection witli Di-. tshidl s' mtcirsi in-' and nnportant 

 pro]>osals concerning gmcti;' (K.iiirnclai ui'<'. attention should 

 be called to a situation wlm-li nriilicf iliese proposals nor the 

 terminology m general iisr ivr(,n i, ,/,.. \\ is customary to refer 

 to individuals carrviiig siiml'> \ or / cliromosomes, as being 

 hetrrozv-iius tor scxdinked u-enes. For some time this has 

 se.'HKd to ho ill-;olvisod jo the writer. 



Thr situation pivvailing in an XX or ZZ individual hetero- 

 /X _ lis I .1 I s> X Imk.d ucne cleaily differs fiom that of an XY 

 'or .\(>i. (.r a Z\\ individual m the vast majority of cases, 

 tlioo.-li Schmidt s work on Lebistes reiiculatus, to which Dr. 

 ( ;isilo I'l-cnil Iv ridh'(i the attention of American workers, pos- 



alwaxs ditfoi- In thi' oiio c.-isr nsiijillv tlicre is a demonstrable 

 alh'h iiiorph. ikM im I rtMnieiit I\- coinpri i! ivo enough m its expres- 

 sion f. pr<.<liir.' iiH.ro "V \<'^< of .in iiiloniiediacv between the 



hi onlei- io ri>ri;otiize this puliation, and m a measure de- 

 seriiie It \viih(Hi; iismu- presence atnl ahsenee terminology, and 

 in iiannnnv with tlie terms onp'-'l l>^ Dr. ^Imll, I should 

 like tn <n— c.t the noun Innninrris >n lialf vokin-) and the 



