ASPECTS OF KINETIC EVOLUTION 349 



ably but magnified images of what occurs among the specific 

 qualities of the milder crosses. The interesting possibility arises 

 that if fertile hybrids can be secured from widely different 

 species the plasmas of which must be more incompatible than 

 those of nearly related forms, such hybrids will give rise to 

 offspring in which there is reversion, not only of one character, 

 but of many or all characters in the same individual, due to a 

 more thorough segregation of the parental germ-plasm as a 

 whole. In other words, the farther apart the parent species 

 are, the more complete will be the return in any given offspring 

 which shows reversion." l 



Instead of representing germinal incompatibility, the Men- 

 delian phenomena may prove to be merely examples of the 

 preservation of welcome and desirable contrasts. Nor is it 

 unreasonable to suppose that the polarity or other form of alter- 

 native reaction is rendered more definite and intense by the 

 process of inbreeding which is considered a necessary prelimin- 

 ary for the exhibition of the Mendelian phenomena. Con- 

 trary to Dr. Guyer's supposition, the " disjunction " of characters 

 does not appear to depend upon the extent of diversity, but upon 

 conditions of inbreeding. Experiments with Mendelism seem 

 to succeed only with closely inbred domesticated varieties, not 

 with wild species. Indeed, it is only among narrow-bred do- 

 mesticated varieties that materials for such experiments can be 

 found, that is, definitely contrasted pairs or small groups of 

 uniform characters. 



SEXUALITY OF CONJUGATE ORGANISMS. 



The sexual differentiation of the higher plants and animals 

 affords another fairly definite indication that sexual and other 

 alternative characters are determined by some such general 

 principle as polarity, rather than by specialized character-unit 

 mechanisms of the reproductive cells. It is now known that the 

 bodies of higher plants and animals are not the result of a com- 

 pleted conjugation of the parental sex-cells, but are formed be- 



1 Guyer, M. F., 1903. The Germ Cells and the Results of Mendel. Cincinnati 

 Lancet-Clinic, May 9. 



