26 



JOl^NAL OF THE RO^ AL llORTI (^r LTTRAL SOC^Tl-yrV. 



|vi-efer, tlieM'ofcv'e, to roi^nrd " prt'scMicc' " mikI " nliscMicc' " of (alliK^ss :is 

 the two ooMl rasi iii^i;- rliaraotoi's, ratlicr than tallncss and dw iirl'ncss. At 

 first sight tliis may appear to be a (hstiiictnui w ithout a dilTtMcMu-e. Hut 

 in rcahty the dirt'ereiice is important and promises to lead to tar-i'eaeJiing 



II 







Bl 



it.) 



DO 



_ X _ 



DO ' 



A 







(A) 



Fig. 14. — Further illustrating Mendelian Segregation. 

 (Also "presence" and "absence.") 



consequences, for it means that each heritable factor is a unit that may 

 be distinct in its inheritance from all other factors. It is simply in its 

 presence ' ' and ' ' absence ' ' that each heritable factor follows 

 Mendel's law. The two diagrams above wall also serve to illustrate the 

 "presence and absence" method (figs. 13 and 14). In these the 



