292 



SCIENCE 



LN. S. Vol. XL. No. 1026 



sub-epidermal layer of a plant — the layer 

 from which the germ-eells 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 represen- 

 tation. 



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 twenty years ago must have 

 seemed inconceivable. For example, the 

 two sets of sex organs, male and female, of 

 the same plant may 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 mongrel, throwing 

 off eggs of a distinct variety in addition to 

 those of its own type; characteristics, 

 essentially independent, may be associated 

 in special combinations which are largely 

 retained in the next generation, so that 

 among the grandchildren there is numerical 

 preponderance of those combinations which 

 existed in the grandparents — 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 polarity, 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 sceptical 

 as to the occurrence of segregation solely 

 in the maturation of the germ-cells,* pre- 

 ferring at present to regard it as a special 

 case of that patch-work 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 Fj ratios of the 

 cereals, for example, is a consequence of 

 very late segregation, whereas the excessive 

 irregularity found in other cases may be 

 taken to indicate that segregation can 

 happen at earlier stages of differentiation. 

 The paradoxical descent of color-blind- 

 ness and other sex-limited conditions — 

 formerly regarded as an inscrutable caprice 

 of nature — has been represented with ap- 

 proximate correctness, and we already know 

 something as to the way, or perhaps I 

 should say ways, in which the determina- 

 tion of sex is accomplished in some of the 

 forms of life — ^though, I hasten to add, we 

 have no inkling as to any method by which 

 that determination may be influenced or 

 directed. It is obvious that such discov- 

 eries have bearings on most of the prob- 

 lems, whether theoretical or practical, in 

 which animals and plants are concerned. 

 Permanence or change of type, perfection 

 of type, purity or mixture of race, "racial 

 development," the succession of forms, 

 from being vague phrases expressing mat- 

 ters of degree, are now seen to be capable of 

 acquiring physiological meanings, already 

 to some extent assigned with precision. For 



4 The fact that in certain plants the male and 

 female organs respectively carry distinct factors 

 may be quoted as almost decisively negativing the 

 suggestion that segregation is confined to the re- 

 duction division. 



