234 Atkinson. 



characters, and the result is a blending of these characters. In the 

 case of the two segregates, hyhrida pijcnella and hijhrida tortuosa, cer- 

 tain groups of the linked factors or tendencies are so situated that in 

 some eggs one combination forms a working relation, while in other 

 eggs another combination succeeds in effecting an organization. The 

 material representing the groups of characters not entering into any 

 one working combination, may then be left beliind in the first suspensor 

 cell of the embryo, or cast out in the cytoplasm, or may become 

 subordinated. The material in the first suspensor cell, as is well 

 known, plays no part in the formative processes of the new individual, 

 since this cell is side-tracked by the basal wall formed during the first 

 division of the zygote. That chromatic materials, or whole chromosomes, 

 are sometimes thrown out in the cytoplasm, and that there also occurs 

 an unequal distribution of chromosomes to opposite ends of the spindle 

 has been abundantly demonstrated. It occurs particularly at critical 

 periods in the ontogeny, for example in raeiotic divisions of certain 

 hybrids (Rosenberg, 1904, 1909) and mutating plants (Gates, 1914).. 

 The zygote of the first generation of interspecific crosses is certainly 

 a critical period in the ontogeny, and the number of cases known 

 where various hybrid types arise in the Fi generation is strong evidence 

 in support of a hypothesis for some sort of erratic behavior of the 

 cellular structures from widely different parentage when they first meet 

 in the zygote. 



This theory of a differential division or sorting in the zygote is 

 not limited to the idea of the permanent loss of certain parts of the 

 hereditary substance by unequal distribution of chromatin or cytoplasmic 

 elements at the time of the first cell division in the zygote. The division, 

 or separation, of material in which lie the "factors" or "tendencies" for 

 various characters, and their sorting, may take place in such a way 

 that not only do those most favorably situated by chance to organize 

 a working relation make up the complex of directive forces in the mor- 

 phogenic and physiologic processes of the new organism, but the material 

 in which resides the other "factors" not entering into this particular 

 working combination, may thus be rendered inactive, or subordinated 

 to such a degree that the action of these factors is not appreciable to 

 our finite judgment. Or in some cases the effect of the subordinated 

 factors may be expressed in a very slight degree. This may account 

 for the frequent manifestation of red color in the mid vein of the leaves 

 of hyhrida pycnella several times alluded to above. In other cases it 



