1908] GATES—REDUCTION IN OENOTHERA II 
POST-SYNAPTIC STAGES 
Synapsis lasts for a comparatively long time, as shown by the fre- 
quency of its occurrence in the material sectioned. During this time 
the spirem shortens and thickens and then begins to arrange itself 
more loosely in the nuclear cavity. This shortening and thickening 
is progressive (figs. 16-18) and apparently continues for some time. 
During these stages the thickness of the spirem may be nearly uniform 
throughout, or it may vary greatly, giving a moniliform appearance, or 
the spirem may appear irregularly constricted at varying intervals. 
In other cases, with a certain depth of stain it is seen to be composed 
of lighter and darker areas more or less regularly alternating. Por- 
tions of the thread may appear homogeneous or may show the lighter 
and darker areas, according to the depth of stain (fig. 17). In more 
deeply stained nuclei, such as fig. 16, the thread appears homogeneous 
throughout. These darker areas are the chromatin discs or chromo- 
meres of various authors; and they give the thread a very character- 
istic appearance. During this well-defined stage the greatly thickened 
spirem is loosely distributed in the nuclear cavity. Deeply staining 
bodies still appear attached to or enmeshed in the coils of the thread. 
At this time one finds undoubted indications of parallel threads. 
When represented by camera drawings in one plane the evidence for 
this is not so satisfactory as in the original preparation, but there is no 
doubt of their occurrence. As already stated, in the earlier stages 
previous to and during synapsis, parallel threads could not be observed, 
and it has not been determined whether they were really absent or 
whether the failure to observe them was due to their extreme delicacy. 
Hence it cannot now be stated whether they have arisen through an 
approximation of spirems at an earlier period, or through a split in the 
single continuous spirem. This matter will be discussed later. 
Following this stage a second well-marked contraction takes place 
(figs. 18, 20, 21), apparently quite as typical and constant in its occur- 
rence as the first contraction stage, which is ordinarily identified as 
Synapsis. This contraction is of much shorter duration, however, 
and entirely different in. appearance, owing to changes which the 
thread has undergone since synapsis, resulting in a. great amount of 
shortening and thickening of the spirem. MOorTTIER (20) has recog- 
nized this.second contraction stage -in Podophyllum, Lilium, and 
