theless, they may have been connected by a fine and invisible thread of protoplasm, for on two other occasions, whilst one mass was rapidly increasing, and another in the same cell rapidly decreasing, I was able, by varying the light and using a high power, to detect a connecting thread of extreme tenuity, which evidently served as the channel of communication between the two. On the other hand, such connecting threads are sometimes seen to break, and their extremities then quickly become club-headed. The other sketches in Fig. 8 show the forms successively assumed.
Shortly after the purple fluid within the cells has become
aggregated, the little masses float about in a colourless or
almost colourless fluid; and the layer of white granular
protoplasm which flows along the walls can now be seen much
more distinctly. The stream flows at an irregular rate, up
one wall and down the opposite one, generally at a slower
rate across the narrow ends of the elongated cells, and so
round and round. But the current sometimes ceases. The
movement is often in waves, and their crests sometimes
stretch almost across the whole width of the cell, and then
sink down again. Small spheres of protoplasm, apparently
quite free, are often driven by the current round the cells;
and filaments attached to the central masses are swayed to
and fro, as if struggling to escape. Altogether, one of these
cells with the ever-changing central masses, and with the
layer of protoplasm flowing round the walls, presents a wonderful scene of vital activity.
Many observations were made on the contents of the cells whilst undergoing the process of aggregation, but I shall detail only a few cases under different heads. A small portion of a leaf was cut off, placed under a high power, and the glands very gently pressed under a compressor. In 15 m. I distinctly saw extremely minute spheres of protoplasm aggregating themselves in the purple fluid; these rapidly increased in size, both within the cells of the glands and of the upper ends of the pedicels. Particles of glass, cork, and cinders were also placed on the glands of many tentacles; in 1 hr. several of them were inflected, but after 1 hr. 35 m. there was no aggregation. Other tentacles with these particles were examined after 8 hrs., and now all their cells had undergone aggregation; so had the cells of the exterior tentacles which had become inflected through the irritation transmitted from the glands of the disc, on which the transported particles rested. This was likewise the case with the short tentacles round the margins of the disc,
