i 9 o8] GATES— REDUCTION IN OENOTHERA 9 



same condition is observed during synapsis, which is found in the 

 same sections. In places the nuclear membrane has either disap- 

 peared or is too delicate to be observed. The cytoplasm, however, 

 retains the original outline of the nucleus. Mottier (20) has 

 apparently observed similar conditions of the nuclear membrane at 

 this time. In some cases it is ruptured and a portion of it is actually 

 carried inward with the nuclear reticulum at the beginning of the 

 contraction (fig. 12). One is tempted to explain this as an artifact; 

 but that this is not the explanation is shown by the considerations 

 already mentioned. The explanation appears to be that as contrac- 

 tion proceeds a portion of the nuclear membrane may be torn away 

 and carried inward attached to the threads. Frequently in these 

 stages one finds the nuclear membrane present on one side of the 

 nucleus but invisible elsewhere. This is the case in fig. 12, although 

 the membrane was drawn as though complete. Observations of other 

 nuclei bear out this interpretation, the nuclear membrane being clearly 

 visible in some cases attached to portions of the reticulum which have 

 contracted far away from the original position of the nuclear wall. In 

 the late prophase, when the definitive chromosomes are formed, a 

 distinct and perfect nuclear membrane is invariably present, so it 

 would appear that in such cases as those just described a new mem- 

 brane is afterward formed. 



Mention must now be made of the chromatic staining material of 

 the nucleus during these stages. The nucleolus is frequently, though 

 not always, included within the synaptic knot. There is a tendency 

 for other dark-staining bodies to accumulate near the periphery of 

 the nucleus (figs. 12, 14) ; as contraction proceeds these are swept in 

 by the reticulum. The exact relation they bear to the threads is not 

 known. In some cases they appear, in the later stages of contraction 

 at least, to form a part of the threads themselves, in other cases they 

 appear to be merely inclusions in its coils. These bodies show no 

 constancy in number, size, or shape. As the spirem takes on the ap- 

 pearance of the synaptic knot, they are still found in its meshes, and 

 portions of the thread itself may also stain darkly, suggesting a 

 solution of a part of their substance and its transfer into the thread. 

 Even when the greater part of the spirem is completely decolorized 

 certain portions of it retain the stain. This appears to be partly 



