330 _ BOTANICAL GAZETTE [way 
importance and significance of the synapsis stage, even though this 
condition is unique in the life cycle, has been greatly overestimated; 
and that the difference between the prophase of an ordinary somatic 
mitosis and that of the heterotypic mitosis (that is, the presynap- 
tic and postsynaptic stages, from the resting reticulum of the 
last somatic mitosis to diakinesis) is much less fundamental in 
character than generally assumed in the current literature. The 
main fact of reduction, according to the most careful studies of 
either the telosynaptic or the parasynaptic method, is that in the 
heterotypic mitosis, instead of dividing, the chromosomes (which 
represent whole somatic chromosomes) segregate. Nor is there 
any adequate evidence that the mechanism of meiosis is meant to 
accomplish anything more than this. The reduction divisions have 
been studied without sufficient comparison with somatic mitoses, 
and it is probable that various features of the postsynaptic stages 
will be found to be devoid of any greater significance than attaches 
to corresponding spirem stages in the prophases of ordinary mitoses. 
Theories based on a supposed interchange of “ chromomeres”” OF . 
other materials during certain stages of the heterotypic prophase 
can be cast aside as having no cytological foundation in critical 
observation. The most careful recent studies have failed, not only 
to find any evidence for an interchange of chromomeres, but eve? 
to substantiate the idea that the chromatic thréads are composed 
of linin in which chromatin granules are imbedded. The careful 
observations of Gricorre and others have served to show that the 
threads are composed of one general material, the varying density 
or alveolation of which may give the appearance of granules. 
heterotypic mitosis as representing the two edges of a single alveolated chromosome, 
and therefore equivalent to the similar paired structures in any somatic prophase, — 
The apparently greater definiteness of the zygonema threads, however, would perhaps 
indicate that the structures represented in the two cases are not necessarily always the 
same. Regarding the synaptic pairing she says: “The important point which Gal- 
tonia demonstrates is that its spireme is univalent. Whether these univalent strands 
join with their homologous pairs telosynaptically or parasynaptically, 
other intermediate method between these two extremes, resolves itself mer 
question of non-essential detail.” Since Galtonia is a ital having both long and short 
chromosomes, this perhaps accounts for the great variety observed in the method of 
pairing. Possibly if the individual chromosomes can be followed it may be found that 
te — ones are more likely to pair parasynaptically and the short ones telosynaP- 
tically. : : 
ely into 4 
