1908] GATES—REDUCTION IN OENOTHERA 23 
Galtonia and Tradescantia, a longitudinal split appears in the thick- 
ened thread, and the double spirem thus formed breaks transversely 
into the reduced number of chromosome pairs. Later, in these 
forms, a secondary union between the chromosomes is claimed to take 
place, forming a single connected chain of chromosomes (as in Oeno- 
thera). Sometimes a pair of chromosomes lies free by itself at this 
time. Then by further shortening the chromosomes of Galtonia 
again fall apart into pairs, though in Tradescantia they frequently 
remain connected even after spindle formation. .The apparent 
similarity of the chromosome chain thus described by MrivaKE in 
Galtonia to the condition in Oenothera, led the writer to make an 
endeavor to harmonize the two accounts. But instead of this, all 
the evidence obtained from a critical study of the stages concerned 
shows that in Oenothera a single very thick spirem breaks transversely 
into the sporophyte number of chromosomes. A critical examination 
of figs. 22-28 will make it clear, I think, that we are following the 
progressive segmentation of a single spirem, and there is no room 
for stages between, in which a double spirem breaks into two parallel 
series of chromosomes. Moreover, it is hardly likely that secondary 
fusions between chromosomes would take place to such an extent as is 
shown in jigs. 23 and 24. In nuclei such as fig. 20, in which a pair of 
chromosomes is cut off prematurely from the spirem while still in the 
second contraction, they are invariably connected at one end and 
rarely, if ever, at the other (though sometimes the close approximation 
of the latter ends may give the false appearance of a ring). This 
would not be the case if they came from separate paired threads 
merely lying side by side, so that this connection shows them to have 
€en really successive on the spirem. From this evidence the writer 
cannot see how anything except a distortion of the facts can lead to the 
assumption in Oenothera of two parallel threads breaking into chro- 
mosomes. Hence the conclusion is that the double threads appear- 
ing in the stage represented by fig. 17 have united to form a single 
thread, which then breaks transversely into the sporophyte number 
of chromosomes, 
This corresponds fairly well with STRASBURGER’S 1904 (30) account 
of the post-synaptic stages in Galtonia, and suggests to the writer 
that perhaps after all the earlier account may be nearer the facts, 
