124 
L. Digby 
It is not wise to attach undue significance to the fact that the num- 
ber of tlie cliromatic bodies in resting tetrad nnclei may be identical 
■\vitli that of the chromosomes, for the niimber of the chroniatie bodies 
is inconstant, and niay be often less than that of the chromosomes. 
Alternative series of presynaptic stages. 
The fact that the polten mother-nuclei of Crepis virens show two 
distinct tj-pes of presynaptic phases has already been mentioned (see 
p. 115), but in Order that the two methods may be clearly distinguished 
from one another only the description of that series characterised by the 
definite but debatable chi’omatic aggregations has been incorporated 
into the account of the meiotic phase. 
Both types are so distinct in character that there is no difficulty in de- 
ciding along which conrse the nuclei of any one particidar bnd are proceeding. 
The fundamental difference between the two series is based on the 
distribution of the chromatic contents. IMiereas in the ‘chroniatie body 
series’, the chromatin is concentrated into a few definite masses, in the 
‘finer reticulate series’, it is distributed in the form of small beads. Both 
may be found in the same flower head but apparently not in the same 
bud. It is believed that the finer distribution of chromatin occurs more 
frequently than the coarser distribution. This would account for the fact 
that Beer (3) did not chance upon the definite chromatic aggregation 
type of prophase, but describes the presynaptic nuclei of certain Compo- 
sitae including C. virens as having a somewhat “coarse network with 
clironiatin aggregates which are irregulär in size and form, and of no 
constant number” (3, p. 707). 
The difference in the two types of pres^niaptic prophases probably 
originates in the late telophase, when, instead of the chromatin of the 
reticulum condensing to form the definite chromatic masses, it remains 
distributed as smaU beads or granules throughout the nucleus. Occa- 
sionally these beads concentrate into larger aggregations (fig. 102) but 
as a rule they remain individually distinct. 
The linin fonns a beautiful reticulum with the chromatin beads situated 
on its Strands, and at the points of intersection (fig. 103). The threads, 
with their beads, are arranged in pairs (figs.103 and 104) and this pairing 
becomes more accentuated as the nucleai’ contents are increasingly ag- 
gregated preparatory for synapsis (figs. 105 and 106). 
It is not possible, for reasons already given, to trace the origin of this 
pairing back to the telophasic fission of the preceding mitosis. It can 
only be assumed from comparative investigations, and from the clear 
