1913] OSTERHOUT—PROTOPLASMIC CONTRACTIONS 449 
of contraction vary somewhat, but in general the variations in true 
plasmolysis are of the same sort as in what may be conveniently 
called the false plasmolysis. We may use the term “false 
plasmolysis”’ to designate not only the contraction produced by 
distilled water but also that which is caused by 
hypotonic solutions. 
The contraction may a place rather 
slowly, in many cases requiring half an hour or 
more to reach the stage shown in fig. 4. True 
plasmolysis may take place much more rapidly. 
But this distinction does not hold generally, for 
in many cases contractions which closely simulate 
true plasmolysis may take place with great 
rapidity. To give a single example of this, the 
behavior of the colorless terminal cells and of 
hairs of Polysiphonia violacea’ may be described. 
On being irrigated with distilled water these 
cells contract very rapidly, so that at the end 
of two minutes they reach the stage shown at 
the right in fig. 6, in which they are practically 
indistinguishable from cells’ plasmolyzed by 
hypertonic sea water or hypertonic sugar solu- 
See tions. The older cells reach the same stage 
Fic.6.—Surface more slowly and betray by the alteration of their 
view of the endofa chromatophores that they are undergoing false 
plasmolysis. It should be noted that by apply- 
in natural condition; ing hypertonic solutions of many salts, both 
attheright after true and false plasmolysis may be produced 
treatment for two simultaneously. These contractions are (as a 
tilled water (dia- Tule) irreversible, at least as soon as they have 
grammatic). passed a certain stage. | 
The effects which have been described as due 
to distilled water were also produced by water taken directly from 
ponds, rivers, and springs; they are not due, therefore, to toxic 
substances resulting from the process of distillation; this point is 
emphasized because attention has previously been drawn to the 
3 Kindly identified by Dr. W. G. FarLow. 
