62 DROSERA ROTUNDIFOLIA. Cuap. ITI. 
the glands,—by the glands absorbing various fluids or 
matter dissolved out of certain bodies,—by exosmose,—— 
and by a certain degree of heat. On the other hand, 
a temperature of about 150° Fahy. (65°5 Cent.) does 
not excite aggregation; nor does the sudden crushing 
of a gland. If a cell is ruptured, neither the exuded 
matter nor that which still remains within the cell 
undergoes aggregation when carbonate of ammonia is 
added. A very strong solution of this salt and rather 
large bits of raw meat prevent the aggregated masses 
being well developed. From these facts we may con- 
clude that the protoplasmic fluid within a cell does 
not become aggregated unless it be in a living state, 
and only imperfectly if the cell has been injured. We 
have also seen that the fluid must be in an oxygen- 
ated state, in order that the process of aggregation 
should travel from cell to cell at the proper rate. 
Various nitrogenous organic fluids and salts of am- 
monia induce aggregation, but in different degrees 
and at very different rates. Carbonate of ammonia is 
the most powerful of all known substances; the ab- 
sorption of +y;s57 of a grain (000482 mg.) by a gland 
suffices to cause all the cells of the same tentacle to 
become aggregated. The first effect of the carbonate 
and of certain other salts of ammonia, as well as of 
some other fluids, is the darkening or blackening of 
the glands. This follows even from long immersion 
in cold distilled water. It apparently depends in 
chief part on the strong aggregation of their cell- 
cuntents, which thus become opaque, and do not 
reflect light. Some other fluids render the glands of 
a brighter red; whilst certain acids, though much 
diluted, the poison of the cobra-snake, &c., make the 
glands perfectly white and opaque; and this seems to 
depend on the coagulation of their contents without 
