Gates.—Pollen Formation in Oenothera gigas . 
935 
Summary. 
In this study of pollen development in Oenothera gigas , several special 
features of synapsis are emphasized. At the beginning of synapsis there 
is a rather sudden increase in the volume of the nucleus, there being in 
some cases a distension of the nuclear membrane and in other cases 
a rupture of the membrane and accumulation of karyolymph in the 
cytoplasm. The nuclear reticulum finally floats freely in the karyolymph, 
and then the rearrangement of the chromatin material from the reticulum 
to the spireme condition takes place. 
Following this there is, at least in some flowers but probably not in alb 
an extrusion of chromatin from the nucleus of one mother-cell through 
cytoplasmic connexions, into the cytoplasm of an adjacent mother-cell. 
For this process I have suggested the name cytomyxis. Probably the 
nucleus always moves to one side of the cell at this time, but this may or 
may not be followed by extrusion of chromatin. 
The extruded chromatin accumulates in a mass after passing through 
the cell wall. A clear liquid appears around these masses, and a membrane 
delimits the clear area from the cytoplasm, forming what I have called 
a pseudo-nucleus. 
Later, these masses loosen up, and acquire an appearance very similar 
to a spireme. The membrane afterwards disappears and the extruded chro¬ 
matin finally appears to be incorporated with the surrounding cytoplasm. 
It is evident that this process may have an important bearing on 
current conceptions of the life cycle and heredity, and on the theory of 
chromosome individuality. It is not improbable that various features 
of the finer morphology of the nucleus depend upon the physical condition 
of aggregation of the nuclear contents, rather than upon autonomous 
self-propagating ‘structures’ as such. 
After the chromatin extrusion has taken place, the nucleus moves back to 
the centre of the cell and undergoes various other transformations during the 
remainder of the period known as synapsis. The most conspicuous of these 
is one in which the larger part of the chromatin content of the nucleus is 
in the form of intertwining chromomeric threads which line the nuclear 
membrane. 
The chromosomes are loosely arranged in the equatorial plate of the 
heterotypic spindle. As they pass to the poles they frequently undergo 
a split, which in some cases gives evidence of being transverse, in others 
longitudinal. 
In one flower examined, two of the anthers exhibited constant differences 
in their mother-cells. In one anther all the mother-cells had smooth walls 
and the (homotypic) spindles were very narrow. In the other anther the 
