A Comparative Study of the Chromosomes etc. 
283 
In Anopholes (Stevens ’ll) both members of the heterochromosome 
pair are united to the ends of a long pair of autosomes. Examination of 
the diploid groups showed that these heterochromosomes are of unequal 
size in the male and equal in the female. In the first spermatocyte division, 
they may be seen as two knobs at the opposite extremities of a long 
autosome geminus fornied from the two chromosomes to which they were 
connected in the spermatogonia. This would indicate, under the assump- 
tion that the pair of idiochromosomes equals xy+y, that “^-chromatin” 
and “auto-chromatin” are not antagonistic. 
In Nezara hilaris there is a pair of idiochromosomes nearly equal in 
size, but in Nezara viridis the y-chromosome is very small, the a:-chromo- 
some about the same size as that of N. hilaris (Wilson ’lOa, ’lla). 
Should it be proved that the “i/-chromatin” is taken up by the autosomes, 
N. hilaris might represent an intermediate form, which one might expect 
to find between two forms such as E. Unotata (with x equal to y in size) 
and E. curvata (with only x). 
5. The unpaired sex-chromosome or heterotropic chromosome may 
be associated more or less intimately wüth one or more autosomes. In 
the Orthoptera McClung (’05) and Sinety (’Ol) have shown that the 
a^chromosome may be connected to one end of an autosome geminus 
in the maturation divisions. In Ascaris megalocephala (Boeing ’09, 
Boveri ’09, Edwards ’IO) the a>element is recognizable only occasion- 
ally, being usuaUy fused to an autosome. This may also be the explanar 
tion of the asymmetrical tetrad of Ascaris felis (Edwards ’ll). In other 
Cases there are heavy fibers connecting the ic-element to one or more 
autosomes in the maturation divisions (Davis ’08, Fig. 91, Plate VI; 
Demoll ’12, Fig. 43, Taf. VI). This was also true of E. curvata and 
probably accounted for the lagging and lengthening of the Orelement. 
FinaUy, the archromosome may be entirely independent of the autosomes. 
It may lie in a separate vesicle during the growth period of the sperma- 
tocyte, take a position outside the spindle in the maturation divisions, 
and tend to form a nucleus of its own (Sutton ’02, Baumgartner ’04, 
Davis ’08, Brunelli ’09). 
Following out the preceding considerations, I have attempted to 
suggest in a diagrammatic way (Plate XXII) how the unpaired 
ic-chromosome of E. curvata may have arisen from the allosome pair of 
E. bimtata. In these diagrams are included the macrochromosome pair, 
one of the eight smaUer autosome pairs, the allosomes and the chromatic 
nucleoli. As far as possible, within the limits of diagrammatic clearness, 
the typical form of the chromosomes in the given stages is adhered to. 
