Meiotic Mitoses of Osmunda . 143 
The material of this investigation suggests that the resting phase is 
eliminated more frequently than not, and consequently that the majority of 
the nuclei pass directly from the telophase of the last archesporial division 
into the heterotype prophase. This may be accounted for by the fixing of 
the material having been done solely on warm, growing days at about noon, 
presumably under conditions of most rapid growth ; possibly if they had 
been fixed under less congenial circumstances there might have been a pre- 
ponderance of resting phases. 
It is proposed to trace the course (1) of those nuclei that pass directly 
from telophase into prophase, (2) of those that pass through an interkinetal 
rest before entering upon prophase. 
(1) In those nuclei that pass directly from telophase into prophase no 
complete separation of the chromosome halves (threads) occurs, but traces of 
paired threads persist. . These, therefore, establish the identity between the 
parallel threads of the telophase of the last archesporial division (derived 
from the longitudinal splitting of the chromosomes) and the parallel threads 
of the heterotype prophase, and accordingly testify to the nature of each 
thread of a pair as representing that of half a univalent chromosome (see 
Text-fig., Nos. 12, 14, and 15). 
Fig. 33 is a nucleus in the transition between the telophase of the last 
archesporial division (PI. VIII, Fig. 29) and the heterotype prophase (PI. IX, 
Fig. 36). Some of the linin threads run in pairs, and some of the chromatic 
beads are arranged in groups of two and four. Three nucleoli persist. In 
the next stage (Fig. 36) the clijmps of beads have dispersed, leaving a more 
even reticulum and the general aspect of the nucleus is that of prophase. 
(2) Following on the late telophase as shown in Fig. 29, the nucleus 
may enter the resting stage. Complete rest (PI. IX, Fig. 34) is characterized 
by an even distribution of granules and fine threads throughout the nucleus, 
forming a close, colourless, foam-like reticulum with the chromatic staining 
contents almost entirely relegated to the nucleoli. The passing of rest into 
very early prophase (Fig. 35) is recognized by the somewhat more sharply- 
staining reticulum, by the appearance of chromatic staining granules, and by 
the generally more active character of the nucleus, thus causing it to be 
sharply defined from the surrounding cytoplasm as compared to its indistinct 
contour when in rest. This stage leads on to that of Fig. 36, in which 
a decided increase in the size of the nucleus has taken place, and the meshes 
of the reticulum have become extended, showing beads and fine threads 
joining the beads together. 
Heterotype or First Meiotic Division. 
In order that the phenomena concerning chromosome formation in the 
two divisions constituting the meiotic phase may be clearly understood, it 
