HitTcHcock: DIFFERENTIAL STAINING 377 
solution passes directly through the outer membrane and the 
rotating protoplasm, without coloring or affecting them in any 
way, so far as can be observed. It also passes through the vacuole 
wall. Apparently some ingenuity will be required to explain 
the observed phenomenon by osmotic action. One is inclined to 
regard it as indicating a general permeability of the tissues to the 
colored solution, which happens to be one not injurious to life 
processes. The color is strongly held in the vacuole and in un- 
colored water cyclosis continues for many days. 
Perhaps it is true, as some have supposed, that living proto- 
plasm will not take up coloring matter. We are told that when 
the nucleus stains the cell is dead. We have seen, however, that 
protoplasm permits passage of the coloring matter used in these 
experiments. Should we, then, conclude, that the contents of 
the vacuole which stain so deeply are therefore dead matter? 
Such a view is not sustained by the observed active circulation 
of the colored cell sap along the definite lines established. 
A PECULIAR PLASMIC STRUCTURE IN THE NITELLA CELL 
Among the many corpuscular elements of the cytoplasm, of 
which we have almost no understanding, some are of such remark- 
able character as to justify particular mention, although they 
cannot yet be satisfactorily described. They are curious spherical 
masses of granular matter, of extreme plasticity, greatly varying 
in size up to 0.1 mm. in diameter. The granules are in a state of 
constant agitation, as though the mass were seething with life. 
Within these spheres may be seen from one to twenty or more 
concave, saucer-shaped disks, 5-15 u in diameter, with contours 
more or less irregular, in rapid rotation, like so many wheels. 
They move freely about in the sphere, constantly changing the 
plane of rotation, sometimes on edge, sometimes lying flat but 
always twisting about and changing position. The nature of the 
movement is suggestive of cilia, but thus far none have been 
detected. 
These have seemed to me as perhaps connected with the de- 
velopment of chloroplasts, many of which are found freely circu- 
lating in the cytoplasm. Although this suggestion rests upon a 
very weak foundation, I find it difficult to resist the impression 
from observations up to this time. 
