1 53 
Meiotic Mitoses of Osminda. 
chromosome split into its daughter halves, but the daughter halves them- 
selves conform to their normal procedure in somatic telophases, and split 
into longitudinal halves (threads). This fact once more illustrates the dual 
nature of each chromosome. 
The splitting of the daughter chromosome halves initiated by the 
fenestration proceeds (Fig. 87) and the identity of the chromosomes is lost 
to view in paired beads and parallel threads (Fig. 88). Simultaneously 
a nuclear limiting membrane makes its appearance. 
In tracing the series of stages between the heterotype telophase and 
the onset of the homotype prophase, the presence or absence of the nuclear 
limiting membrane and the evolution of the cell- plate separating the 
daughter nuclei are found to be useful guides in the reconstruction of the 
sequences. The phases between the two divisions are apparently quickly 
passed through, for it is not uncommon to find heterotype anaphases inter- 
spersed with homotype metaphases in the same sporangium. 
Following the dissolution of the chromosomes comes their reconstruc- 
tion, and this may be regarded as the beginning of the homotype division. 
Homotype or Second Meiotic Division. 
The homotype may justly be regarded as a continuation of the last pre- 
meiotic division , and consequently the heterotype represents an interpolated 
phase in which the numerical reduction of the chromosomes is accomplished. 
The univalent spireme filament of the homotypic prophases is homo- 
logous with the univalent spireme filament of the heterotypic prophases, 
and this in turn is derived from the reassociation of the longitudinal halves 
of univalent chromosomes (threads) that had split apart during the pre- 
ceding telophase of the last premeiotic division. These halves (or threads) 
do not dissociate during the heterotype division, but their separation takes 
place on the homotype spindle (see Text-fig., No. 30). 
The points of difference between a homotypic and a somatic division 
are : (1) the homotype possesses half the somatic number of chromosomes ; 
(2) the homotype is endowed with entire univalent chromosomes from the 
preceding heterotype spindle, instead of with half univalent or daughter 
chromosomes ; (3) the homotype prophases show a very precocious splitting 
of the univalent spireme as compared to somatic prophases, or, in other 
words, the daughter chromosomes, which will separate on the homotypic 
spindle, are dissociated at a very early stage. 
The onset of the homotype prophase is recognized by the chromatic 
contents becoming concentrated into rounded masses in excess of the 
x number of chromosomes (Fig. 89). This is not remarkable, as double the 
reduced number of chromosomes split into longitudinal halves (threads) 
during the preceding heterotype telophase owing to the splitting of each 
entire univalent chromosome into daughter chromosomes (Figs. 84 and 85), 
