(EXOTMKR/V 3[UT. LATA AND (E. MUT. SEMILATA. 
549 
gradually dimiiiisli in size a,nd filially disappear. In an earlier 
paper by one of ns (Gates, 1907a) they were considered 
problematical bodies and provisionally called lieterocliromo- 
somes. Since their origin from nucleoli is now proved, this 
name may be discarded. Fig. 48 also shows a small nucleolus 
persisting on the heterotypic spindle. 
Two other figures represent certain conditions in plant Xo. 
226 . II . 18, having characters intermediate between la ta and 
semi lata. Fig. 53 shows a homotypic metaphase group with 
7 chromosomes, the two halves, in one chromosome particu- 
larly, being rather widely separated. Fig. 54 shows a homo- 
typic meta.phase stage in polar view, in which the right-hand 
group clearly contains 6 whole chromosomes longitudinally 
split, and one half-chromosome. The left-hand group con- 
tains 7-g- chromosomes, and between the groups are fragments 
of the fifteenth chromosome, which is degenerating after being 
left behind on the heterotypic spindle. 
The variety of behaviour thus exhibited by certain chromo- 
somes in these plants include (1) the division of one chromo- 
some (probably the extra one) in the heterotypic mitosis, this 
behaviour sometimes extending to a second, and occurring 
also in 14-chromosome plants descended from 15-chrornosome 
individuals ; (2) the fragmentation and later degeneration of 
certain chromosomes on the heterotypic and homotypic 
spindles ; (3) the loss of chromatin from one or more chromo- 
somes by its trailing behind on the heterotypic spindle ; 
(4) the leaving behind of certain chromosomes, to degenerate 
on the heterotypic spindle ; (5) the formation of extra nuclei 
by lagging chromosomes in the heterotypic and homotypic 
mitoses. 
Discussion. 
From the facts above presented we may conclude, not only 
that the mutants lata and semilata constantly possess an 
extra chromosome, but that whenever, in any race, or species or 
hybrid of Qilnothera, individuals occur having the general 
type of foliage characteristic of lata and semilata, such 
