No. 531] GENOTYPE CONCEPTION OF HEREDITY 153 



only say that this case does not seem incompatible with 

 Mendelian views. It must also be borne in mind that 

 certainly there have been very many ffenodi ffrrrnccs 

 between the differing races intercrossed in Castle's 

 experiments. Hence these experiments are really operat- 

 ing with highly poly-heterozygotic F^generations. And 

 how great influence upon dimensions (of ears and other 

 parts of the body) those color-determining genes may 

 have exercised can not be easily determined. 



As to beans, it is proved that genes, effective in color- 

 reactions, may also have great influence upon the dimen- 

 sions and forms. So in my crosses a special factor, 

 which makes yellow color turn into brown and causes 

 violet to be turned into black, has a very marked influence 

 upon the size and form of the beans in question. Here 

 exact data are not necessary; the instance exemplifies the 

 two incident matters of fact, viz., that apparently simple 

 "dimensional" or meristic characters may be determined 

 by several different genes, and that one sort of gene may 

 have influence upon several different reactions. 



Then it seems that Mendelian analysis is proceeding in 

 a very prosperous way; but there may be even very 

 narrow limits for this analysis : the entire organization 

 may never be "segregated" into genes! But still there 

 is much to do in carrying through the genotype-concep- 

 tion as far as possible. 



As to cytological researches the genotype-conception is 

 as yet rather indifferent. Certainly the process of segre- 

 gation must be a cell-act ion intimately connected with 

 division. But all the innumerably detailed results of the 

 refined cytological methods of to-day do not elucidate 

 anything as to segregation. It seems to the unprejudiced 

 observer that the much-discussed cytological phenomena 

 of karyokinesis, synapsis, reduction and so on may be 

 regarded father as consequences or manifestations of the 

 divisions, repartitions and segregations of genotypical 

 constituents (and all other things in the cell) than as 

 their causes. This view is applicable even in those cases 



