72 EDMUND B. WILSON 



It seems to me that such facts have the value of actual experi- 

 mental evidence in support of the hypothesis of the genetic con- 

 tinuity of the chromosomes and that of their qualitative difference. 

 All will admit that the peculiarities of the later generations of cells 

 in this individual of Metapodius are inherited from earlier ones. 

 It is the obvious, natural and, I think, inevitable conclusion that 

 the third ra-chromosome, introduced at an early period, has not 

 lost its identity in the later stages. If its presence is merely owing 

 to a corresponding excess of chromatin, how shall we account for 

 the characteristic peculiarities of behavior that differentiate it 

 so sharply from an ordinary " supernumerary " of corresponding 

 size? To reply that the excess represents a particular kind of 

 chromatin that is re-segregated at each division in the form of a 

 particular chromosome is to grant the most vital assumption 

 in the hypothesis of genetic continuity. 



I think that sufficient emphasis has not yet been laid upon the 

 support given to this hypothesis by the variable position of the 

 chromosomes in the diploid groups. I have several times pointed 

 out in this paper and preceding ones, that there is no constancy in 

 the relative position of the spermatogonial chromosomes as may 

 be seen with particular clearness in case of the ra-chromosomes of 

 the Coreidse or the small idiochromosome of the Pentatomidae or 

 Lygseidse, or of chromosomes distinguishable by their large size, 

 such as are seen in Protenor, Largus or Anasa. This is certainly 

 not what we should expect were the chromosomes merely " tactic" 

 formations that appear in characteristic array, as a crystal form 

 in a solution, merely because of the specific properties of a single 

 chromatin-substance as such. Two answers might be made to 

 this. It might be said that the chromosomes merely represent 

 the segregation of so many different kinds of chromatin that are 

 mixed together in the resting nucleus. 8 I am disposed to regard 

 this as a tenable hypothesis; but obviously it grants the most essen- 

 tial part of the continuity hypothesis. Again it might be said that 

 the chromosomes are originally formed always in the same j osi- 

 tion but lose it by subsequent shiftings in the prophases. It 



Cf. Fick: '05; Wilson: '09c. 



