932 Gates.—Pollen Formation in Oenothera gig as, 
powers the smallest nuclear elements which exist as distinct elements of 
organic structure. Many of the so-called structural features of the nucleus 
are such as might be assumed by any other colloidal material as well as 
chromatin, under similar physical conditions of aggregation. 
Therefore it seems probable that our present microscope powers already 
disclose all of * structure ’ that is to be found in the nucleus, and the search 
for structure within structure down to and beyond the limits of our present 
powers of magnification is probably a vain one. Chamberlain (’ 09 ) has 
found that in the enormous nuclei in the reproductive cells of Cycads, no 
more ‘ structure within structure ’ is to be seen than in the very much 
smaller nuclei of other plants. The appearance is rather that of a colloidal 
material loosely aggregated. It is not always sufficiently kept in mind that 
the ‘ structures ’ studied in the nucleus represent the coagulation and preci¬ 
pitation figures resulting from certain conditions of distribution of the viscous, 
colloidal chromatin materials in the living nucleus, although these different 
distributions are doubtless in themselves of the highest physiological 
significance. 
This point of view does not imply that the chromosomes are chemically 
alike, and there is much evidence that they are not. Further, in the absence 
of definite observational evidence of self-propagating differential elements 
within the chromosome, it seems best at present to formulate hypotheses 
without making the assumption that such exist. 
It is evident that this process of chromatin extrusion may also have an 
important bearing on our views of chromosome individuality, but it does not 
seem best to discuss this matter further until the significance of the process 
is better understood. Since this process, similar in the main essentials, has 
now been observed in two widely separated genera of Angiosperms, belonging 
respectively to Monocotyledons and Dicotyledons, it will probably be found 
to be of general occurrence. I have used the term cytomyxis to indicate 
that the process is probably one of equalization between different mother- 
cells. It is probable that actual extrusion of chromatin does not always 
occur, but that synapsis may be passed through without it, although the 
movement of the nucleus to the side of the cell probably always does take 
place. This process may have an important significance from the standpoint 
of heredity and the life cycle. A somewhat similar process has recently 
been described by Carruthers (Tl) in the Ascomycete Helvetia , although 
here the extrusion is from the nucleus into the cytoplasm of the same cell, 
and not into another cell. 
The type of sterility here described is an interesting one. The plant 
which showed flowers in this condition also showed normal pollen develop¬ 
ment in other flowers, and its pollen was used successfully in making 
crosses. De Vries mentions (Mutationstheorie, ii, p. 59) that one plant of 
O.gigas in his cultures in 1899 was wholly sterile after repeated artificial 
