Cnar. 1, THE PROCESS OF AGGREGATION. 45 
independently of the absorption of any matter. So it may pos- 
sibly be in the case of the carbonate of ammonia. As, how- 
ever, the aggregation caused by this salt travels down the 
tentacles at a quicker rate than when insoluble particles are 
placed on the glands, it is probable that ammonia in some form 
is absorbed not only by the glands, but passes down the 
tentacles. 
Having examined a leaf in water, and found the contents of the 
cells homogeneous, I placed it in a few drops of a solution of one 
part of the carbonate to 487 of water, and attended to the cells 
immediately beneath the glands, but did not use a very high 
power. No aggregation was visible in 3 m.; but after 15 m. 
small spheres of protoplasm were formed, more especially 
beneath tne long-headed marginal glands; the process, how- 
ever, in this case took place with unusual slowness. In 25m. 
conspicuous spherical masses were present in the cells of the 
pedicels for a length about equal to that of the glands; and 
in 3 hrs. to that of a third or half of the whole tentacle. 
If tentacles with cells containing only very pale pink fluid, 
and apparently but little protoplasm, are placed in a few drops 
of a weak solution of one part of the carbonate to 4875 of 
water (1 gr. to 10 0z.), and thehighly transparent cells beneath 
the glarids are carefully observed under a high power, these 
may be seen first to become slightly cloudy from the formation 
of numberless, only just perceptible, granules, which rapidly 
grow larger either from coalescence or from attracting more 
protoplasm from the surrounding fluid. On one occasion I 
chose a singularly pale leaf, and gave it, whilst under the 
microscope, a single drop of a stronger solution of one part to 
487 of water; in this case the contents of the cells did not 
become cloudy, but after 10 m. minute irregular granules of 
protoplasm could be detected, which soon increased into 
irregular masses and globules of a greenish or very pale purple 
tint; but these never formed perfect spheres, though incessantly 
changing their shapes and positions. 
With moderately red leaves the first effect of a solution of the 
carbonate generally is the formation of two or three, or of 
several, extremely minute purple spheres which rapidly increase 
in size. To give an idea of the rate at which such spheres 
increase in size, 1 may mention that a rather pale purple leaf 
placed under a slip of glass was given a drop of a solution of 
one part to 292 of water, and in 13 m. a few minute spheres of 
protoplasm were formed ; one of these, after 2 hrs. 30 m., was 
about two thirds of the diameter of the cell. After 4 hrs. 25 m, 
