1911] GATES—CHROMOSOME REDUCTION 327 
14 from the O. gigas male cell. In reduction they segregated 
regularly into groups of 10 and 11. The recent work on animal 
species and hybrids with heteromorphic chromosomes, by BovERI, 
Batzer, Hersst, TENNANT, and others, including the remark- 
able cases in which certain chromosomes are extruded, is all a 
confirmation of the same point of view. 
We have thus reached the view that, while the chromosomes 
clearly behave as more or less independent units of structure, we 
are not justified by observational evidence in assuming that they 
in turn are composed of smaller morphological units. Further, 
what has frequently been interpreted as a transverse segmentation 
of the spirem or of the meiotic chromosome gemini is now known 
to be, in most cases at least, only the separation of whole somatic 
chromosomes. It may therefore be questioned whether a trans- 
verse fission of the chromosomes themselves ever regularly occurs. 
As already pointed out, however, this may be for purely mechanical 
or physical reasons. 
From this point of view let us now examine the question of the 
method of chromosome reduction. In former papers (4, 5, 7) 
T have shown that reduction in Oenothera takes place according to 
the FARMER and Moore method of telosynapsis, the spirem seg- 
menting into a chain of chromosomes arranged end-to-end. In 
the heterotypic mitosis these (somatic) chromosomes, which may 
or may not be visibly in pairs, are segregated into two groups at 
the poles of the spindle. Each of these chromosomes undergoes 
a longitudinal split during the anaphase or telophase of the hetero- 
typic mitosis, and the halves thus produced are distributed by the 
homotypic mitosis. The essential and critical stages which show 
that this is the method of reduction in Oenothera were presented 
in my paper of 1908. The suggestion of GREGOIRE, in his very 
useful summary of the literature of chromosome reduction (12, 
P. 325), that a strepsinema stage had been omitted between the 
pachynema and diakinesis, cannot apply. It is evident from an 
€xamination of figs. 18-32 in my paper already referred to (4) 
that such a stage cannot be intercalated. Especially figs. 18, 22, 
23, and 24 leave no room for any other interpretation than the 
obvious one that a pachynema thread is segmenting into a chain 
