37 & Gates and Rees . — A Cy to logical Study of 
chromosomes just beginning to separate. The manner of separation of the 
halves of a bivalent chromosome is shown exceptionally clearly in Fig. 58. 
The spindle is uncut and clearly only seven bodies are present — so that 
this represents a typical case in which two pairs of bivalents have coalesced. 
Figs. 52 and 54 have already shown that the point of spindle fibre attach- 
ment is at one end of the bivalent chromosomes. Obviously, fibres from 
opposite ends of the spindle must become attached close together to each 
half of a bivalent, and at the same end of the chromosome. The appear- 
ance (see Fig. 57) is as if the contraction of these fibres pulled the two 
longitudinal halves gradually apart. Two globular pairs of chromosomes [ 
are already completely separated, a short and a longer pair still remain 
attached by a thread at one end, while in the centre, and less clearly at 
the left side, of the group, two of the longest pairs are being drawn apart. . 
Focusing on the centre pair shows particularly clearly that its central 
thicker portion consists of the ends (in vertical orientation) which have not 
yet separated. Thus five of the pairs have already separated, while the 
other two may each represent two bivalents fused end to end, which would 
possibly account for their lagging. 
Fig. 59 is from a section of a later anaphase in which fifteen or sixteen 
chromosomes are present. Fig. 60 represents an early telophase in which 
the full gametic number (9) is seen in each of the daughter nuclei. Several 
of these chrortiosomes at least have already undergone the longitudinal split 
for the homotypic mitosis and appear as X’s and V’s. The remains of the 
spindle are still visible, and the nuclear membranes appear incomplete on 
the side next the spindle. Some of the chromosomes are already beginning ! 
to anastomose. In Fig. 61 this process is much further advanced and a cell 
plate is being laid down, while Fig. 62 represents the interkinesis stages . 
with a loose and heavy threadwork formed in the nuclei. Abnormalities j 
are sometimes found at this time, in which some of the chromosomes 1 
pass irregularly towards the poles and frequently give rise to extra nuclei 
(Fig. 65). 
• 
Homotypic Mitosis. 
We have observed relatively few stages of the homotypic division, 
which as usual is passed through quickly. In the metaphase, polar view, 
nine univalent chromosomes were counted in some cases. But one spindle 
in side view showed only six chromosomes, connected by darkly . staining 
material. It appears that here also coalescence of chromosomes has 
occurred similar to those of the heterotypic bivalents. But in the absence 
of more abundant material and with the possibility of the treatment having 
affected the preparation, we refrain from further interpretation. The stages 
observed show that in the homotypic mitosis the univalent chromosomes 
undergo a longitudinal split and separation in the usual way. 
