No. 531] GENOTYPE CONCEPTION OF HEREDITY 151 



Here we can not discuss the difficulties in a complete 

 carrying through of the Mendelian analysis; Bateson's 

 recent book contains a richness of instances concerning 

 this matter. Only one instance of special importance 

 may be mentioned here, viz., the so-called "blended in- 

 heritance" opposed to Mendelian segregation or "alter- 

 native inheritance." In cases of blended inheritance the 

 genes in question might be supposed to "fuse together" 

 by the act of hybridization, or, in accordance with the 

 presence- and absence-view, the gene unilaterally carried 

 to the zygote might here in some manner be "diluted." 

 In this way, which certainly is very badly compatible with 

 the conception of genes as unit-factors, failing segrega- 

 tion might be explained. 



Cases of failing segregation seemed to be abundant in 

 the beginning of the modern Mendelian era; Mendel him- 

 self pointed out some typical cases in the speeies-liybrids 

 of Hieracium. And Correns's indication as to the con- 

 stant intermediate stature of maize stems seemed to be 

 a crucial case. Now the insight won by breeding experi- 

 ments as well as by cytological researches concerning 

 the phenomena of apogamy has put the question in a new 

 light. The discoveries of Murbeck, Raunkiaer, < )stcnfeld, 

 Rosenberg and others have led to quite other explana- 

 tions as to the constancy of several intermediate hybrid 

 forms. In such cases no segregation is realized, because 

 no gametogenesis is going on — and in such cases there is 

 no reason for supposing any "fusing" or "dilution" of 

 genes. And as to Correns's experiments, this careful 

 author has himself withdrawn the suggestion in question. 



But still cases of "blending inheritance" remain. 

 Among these Castle's experiences as to the dimensions of 

 rabbits, especially the length of ears, are the most impor- 

 tant and most discussed instances. Castle has in a con- 

 vincing and suggestive manner demonstrated that the 

 complicated color-characters in rabbits agree with the 

 Mendelian laws. Therefore much stress might be laid 

 upon his indication of cases contrary to these laws. 



