1908] GATES—REDUCTION IN OENOTHERA at 
more or less intimately about the time of synapsis or later. After the 
events of synapsis, a longitudinal split reappears in the thickened 
spirem threads, this split representing the line of approximation of the 
two original spirems. Transverse segmentation into pairs of chro- 
mosomes, which are believed to be homologous somatic chromosomes 
of maternal and paternal origin, then takes place. The halves of these 
bivalent chromosomes, which lie side by side, are then distributed 
in the heterotypic mitosis, which is thus a reduction division. In 
the anaphase of the heterotypic mitosis a longitudinal split appears in 
the daughter chromosomes, which is regarded as a premature split 
for the homotypic mitosis, the latter being thus an equation division. 
The persistency with which this general account has been given, not- 
withstanding differences in detail, particularly preceding and during 
synapsis, leads the writer to the belief that it is probably correct in its 
main outlines, at least in many of the forms described. This being 
judged to be the case, every effort was made to bring the account in 
Oenothera into harmony with this general course of events but with- 
out success, for Oenothera is found to deviate in some important 
particulars, as is already evident from the description. 
Another general account of reduction in plants, which was adhered 
to by STRASBURGER as late as 1904 (30), and has been held notably 
by Farmer and Moore (8, 9), FARMER and SHOVE (10), SCHAFFNER 
(28), Morrter (19, 20), and others, to mention only a few of the recent 
papers, is in general as follows: The split in the spirem which occurs 
at about the time of synapsis is a true split, such as may occur in the 
prophase of somatic mitoses, and is not preceded by a pairing of 
parallel threads, but the thread is single from the beginning. This 
split afterward closes up as the thread shortens and thickens after 
Synapsis, and the single spirem so formed segments usually into the 
reduced number of chromosomes, which are thus arranged successively 
end to end. Each such bivalent chromosome thus consists of two 
halves arranged end to end, not side by side, and the heterotypic 
Mitosis thus separates successive whole chromosomes on the spirem, 
being therefore, as in the other account, a reduction division. The 
split which appears in the anaphase of this mitosis is interpreted as a 
reappearance of the earlier longitudinal split of the spirem. The 
homotypic mitosis is therefore an equation or longitudinal division. 
