Guar. XL GENERAL, SUMMARY. 265 
process often is the formation of a dark red, bag- 
like mass of protoplasm, which afterwards divides 
and undergoes the usual repeated changes of form. 
Before any aggregation has been excited, a sheet of 
colourless protoplasm, including granules (the prim- 
ordial utricle of Mohl), flows round the walls of the 
cells; and this becomes more distinct after the con- 
tents have been partially aggregated into spheres 
or bag-like masses. But after a time the granules 
are drawn towards the central masses and unite with 
them; and then the circulating sheet can no longer 
be distinguished, but there is still a current of trans- 
parent fluid within the cells. 
Aggregation is excited by almost all the stimulants 
which induce movement; such as the glands being 
touched two or three times, the pressure of minute 
inorganic particles, the absorption of various fluids, 
even long immersion in distilled: water, exosmose, and 
heat. Of the many stimulants:tried, carbonate of 
ammonia is the most energetic and acts the quickest: 
a dose of +775 of a grain (00048 mg.) given to 
a single gland suffices to cause in one hour well- 
marked aggregation in the upper cells of the tentacle. 
The process goes on only as long as the protoplasm 
is in a living, vigorous, and oxygenated condition. 
The result is in all respects exactly the same, 
whether a gland has been excited directly, or has 
received an influence from other and distant glands, 
But there is one important difference: when the 
central glands are irritated, they transmit centri- 
fugally an influence up the pedicels of the exterior 
tentacles to their glands; but the actual process of 
aggregation travels centripetally, from the glands of 
the exterior tentacles down their pedicels. The ex- 
eiting influence, therefore, which is transmitted from 
