364 ANNUAL EEPOET SMITHSONIAN INSTITUTION, 1915. 



These and hosts of difficult cases remain almost imtoiiched. In par- 

 ticular the discovery of E. Baur, and the evidence of Winkler in re- 

 gard to his " graft hybrids," both showing that the subepidermal 

 layer of a plant — ^the layer from which the germ cells are derived — 

 may bear exclusively the characters of a part only of the soma, give 

 hints of curious complications, and suggest that in plants at least the 

 interrelations between soma and gamete may be far less simple than 

 we have supposed. Nevertheless, speaking generally, we see nothing 

 to indicate that qualitative characters descend, whether in plants or 

 animals, according to systems which are incapable of factorial rep- 

 resentation. 



The body of evidence accumulated by this method of analysis is 

 now very large, and is still growing fast by the labors of many 

 workers. Progress is also beginning along many novel and curious 

 lines. The details are too technical for inclusion here. Suffice it to 

 say that not only have we proof that segregation affects a vast range 

 of characteristics, but in the course of our analysis phenomena of 

 most unexpected kinds have been encountered. Some of these 

 things 20 years ago must, have seemed inconceivable. For ex- 

 ample, the two sets of sex organs, male and female, of the same plant 

 Tasiy not be carrying the same characteristics ; in some animals char- 

 acteristics, quite independent of sex, may be distributed solely or 

 predominantly to one sex; in certain species the male may be 

 breeding true to its own type, while the female is permanently mon- 

 grel, throwing off eggs of a distinct variety in addition to those of 

 its own type; characteristics, essentially independent, may be asso- 

 ciated in special combinations which are largely retained in the next 

 generation, so that among the grandchildren there is numerical pre- 

 ponderance of those combinations which existed in the grand- 

 parents — a discovery which introduces us to a new phenomenon of 

 polarity in the organism. 



We are accustomed to the fact that the fertilized egg has a polar- 

 ity, a front and hind end, for example ; but we have now to recognize 

 that it, or the primitive germinal cells formed from it, may have 

 another polarity shown in the groupings of the parental elements. 

 I am entirely skeptical as to the occurrence of segregation solely in 

 the maturation of the germ cells,^ preferring at present to regard it 

 as a special case of that patchwork condition we see in so many 

 plants. These mosaics may break up, emitting bud sports at various 

 cell divisions, and I suspect that the great regularity seen in the 

 F2 ratios of the cereals, for example, is a consequence of very late 

 segregation, whereas the excessive in-egularity found in other cases 



1 The fact that in certain plants the male and female organs respectively carry dis- 

 tinct factors may be quoted as almost decisively negativing the suggestion that segrega- 

 tion is confined to the reduction division. 



