EDMUXD 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 m-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 sharph^ from an ordinary ''supernumerary" of corresponding 
size? To repl}^ 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 7?z-chromosomes of 
the Coreidae 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 certainh' 
not what we should expect were the chromosomes merely 'Hactic" 
formations that appear in characteristic array, as a crystal form 
in a solution, merel}' 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.^ 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 i osi- 
tion but lose it by subsequent shiftings in the prophases. It 
-8 C/. Fick: '05; Wilson: '09c. 
