(ENOTHEllA MUT. LATA AND (E. MUT. SEMILATA. 
553 
animals, and particularly with the cases where the females 
have one more chromosome than the males, is at once sug- 
gested. In such cases as An as a tristis among insects, the 
males have an odd, unpaired or heterotropic chromosome, 
while in the females this chromosome is present in duplicate, 
and therefore has a mate. In spermatogenesis, half the sperms 
i*eceive the odd chromosome and half do not, while all the 
eggs contain this chromosome. Hence eggs fertilised by a 
sperm containing the odd chromosome produce females in 
which this chromosome is present in duplicate, and eggs 
fertilised by the other class of sperm produce males with an 
unpaired chromosome. 
The case of CR. lata differs from this in several respects. 
In the first place, the extra or fifteenth chromosome is not a 
duplicate, but a triplicate of a pair already present. And in 
the second place this difference in chromosome content is 
associated, not with sex (unless the male-sterility of lata be 
significant in this connection), but with a difference in the 
foliage and various other features of the plant. It is possible 
to say, however, that in these plants the extra chromosome, 
when present as the triplicate of a pair, is constantly associated 
with the development of certain foliage characters, in the 
same way that the accessory chromosome when present in 
duplicate in certain insects is constantly associated with the 
development of the female sex characters. 
In certain respects the extra chromosome resembles more 
closely the supernumerary chromosomes described by Wilson 
(1909, 1910) in Metapodius. Without detailing the rather 
complicated facts in this genus of Hemiptera, it may be said 
that the typical or fundamental number of chromosomes 
is 22 in both males and females, including 18 auto- 
somes, two m-chromosomes, and two idiochromosomes or 
sex chromosomes. Of the latter, the females possess two large 
ones and the males a large and a small. Ahiriations from 
this condition occur, and though the chromosome-number for 
each individual is practically constant, yet in different 
individuals of, e.<j., M. granulosus, the number ranges 
