308 DA VENP ORT. [VOL. I L 



distinguishable in this regard from one of the parents. Inter- 

 mediate conditions do not occur [in alternative heritage]. 



2. In the formation of the pollen and the egg cell the two 

 antagonistic peculiarities are segregated ; so that each ripe 

 germ cell carries either one of these peculiarities. 



Of the two antagonisti-c peculiarities united in the hybrid, 

 that which becomes visible in the soma is called by Mendel the 

 dominating; that which lies latent is called the recessive char- 

 acter. What determines which character shall be dominating 

 is still unknown, and the determination of this point offers an 

 enticing field of inquiry. In some cases the dominating form 

 is the systematically higher; in others it is the older or ances- 

 tral form. 



The law of dichotomy may now be developed. When a 

 hybrid (monohybrid) fertilization takes place the zygote con- 

 tains both the dominant quality (abbreviated d) and the reces- 

 sive quality (/'). In the early cleavages d and r are both passed 

 over into both the daughter-cells ; but apparently, at the time 

 of segregation of the germ cells, the somatic cells are provided 

 with d only, while the germ cells retain both qualities. In the 

 ripening of these germ cells, probably in the reduction division, 

 d and r come to reside in distinct cells, so that we have 



of the female cells 50% d + 50% r, and 

 of the male cells 50% d + 50% r. 



If now hybrids are crossed haphazard, a male d cell may 

 unite with either a female d cell or with a female r cell ; like- 

 wise a male r cell may unite with a female d or a female r cell. 

 Consequently in the long run we shall have of all the zygotes 



25% d,d + 50% d, r + 25% r, ;-, 



or 50^ of the zygotes hybrid and 5o'/< of pure blood, and of the 

 latter half exclusively maternal and half paternal. But since 

 the soma developed from the hybrid germ cell has the domi- 

 nant character, we shall have 



75% of the cases with the dominant character 

 25% " ' " " recessive " 



and this agrees with various empirical results, of which the 

 following from Correns is instructive. A cross was obtained 



