-No. 6421 VARIATION IN DATURA I9 



Bciknced Tvpes 



Unbdldnced Types 



Diploid 





odijiccl Diploid; 



Simple Trtraaomic 



Double Tmo^c 



Triploid 



M 



>di]ied Tnploids 





Tetraploid 



#1iir# 



M 



odified Tetraploids 



^ll^4 





pairs when there are more than 2 in a set) has respec- 

 tively 2, 3, or 4 chromosomes. I have suggested (2) the 

 terms disome, to indicate a set of 2 chromosomes, trisome 

 a set of 3, and tetrasome a set of 4, etc., with the adjectives 

 disomic, trisomic, tetrasomio, ('tc. Sneli torms may be 

 found useful, but it seems inipossil.lr to dt vise a simple 

 terminology that will afleqnatcl\ (locribc cvcii the chro- 

 mosomal irregularities at pi-csnit known In Drosopliila 

 and Datura. Accordin,uT\-, nfter ciuisidrrahlc disciissioii 

 with Dr. Bridges, wo have auTccd upon a set of t'..nniila' 

 which is illustrated in the diagram and which we shall 

 use in our present papers. 



