4 6 Fraser. — Contributions to the Cytology of 
between the longitudinal fission, characteristic of somatic divisions, in the first 
prophase, and the final separation of the split halves in the second metaphase. 
The description of Farmer and Moore is in agreement with that given 
by Schaffner ( 38 ), and has been recently confirmed by Mottier ( 34 ). 
The chief points in which these authors differ from Allen and Berghs 
are, (i) the occurrence of two contraction figures, (2) the approximation 
of the arms of each of the loops formed during synapsis, (3) the breaking 
up of the spireme so that each loop (or some equivalent portion of the 
thread) forms a bivalent chromosome, (4) the consequent transverse fission 
of each chromosome on the spindle. To a great extent the difference in 
interpretation is due to a difference in the seriation of the stages observed. 
It has been suggested by various authors that the divisions in the 
ascus probably correspond to those in the spore mother-cells of higher 
plants, and also that the occurrence of three divisions is in some way related 
to the two nuclear fusions in the life-history of Ascomycetes. 
In 1905, Harper ( 31 ), in his account of the development of Phyllactinia , 
described the two ascus nuclei, at the time of fusion, as each containing 
eight or nine chromatin threads attached to a central body. The centres 
fuse and the chromatin systems become intimately mingled. Synapsis 
takes place, the chromatin becoming contracted towards the central body. 
Later a spireme of eight strands is formed, and gives rise to the eight 
chromosomes of the equatorial plate. The chromosomes divide, and eight 
go to each pole. Eight chromosomes appear in the second and third 
mitoses, and in each case divide so that eight daughter chromosomes pass 
to the poles. These divisions appear to resemble the first, but are not 
initiated by a synapsis. 
Maire ( 33 ), in 1905, described the first divisions in the ascus, in Galactmia 
s?iccosa , Pustularia vesiculosa , and some other species, as respectively 
heterotype and homotype. 
Guillermond ( 25 ), in the same year, investigated the ascus divisions of 
various species, amongst which is Iiumaria (Peziza) rutilans. He describes 
the nucleus of the ascus as rich in chromatin and containing a large oval 
nucleolus. The spireme often shows paired filaments ; it undergoes 
a characteristic synapsis in which the chromatin is condensed at one 
side of the nucleus. Subsequently sixteen chromosomes appear, having 
the forms of U’s or V’s, with short, thick branches ; they become grouped 
in the centre of the nucleus, and an intra-nuclear spindle and centrosomes 
appear ; the asters can only exceptionally be distinguished. In the meta- 
phase the chromosomes split longitudinally, forming hollow c lozenges ’ ; 
the two halves separate, and the V-shaped daughter chromosomes pass 
to the poles. In the anaphase sixteen V- or hook-shaped chromosomes 
were counted at each end of the spindle. On reaching the poles they branch 
and become united end to end, and the daughter nuclei are reconstructed. 
