Chap. III.] THE PROCESS OP AGGREGATION. 37 



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 ten- 

 uity, 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 won- 

 derful 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 placc<i 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 ex- 

 amined after 8 hrs., and now all their cells had undergone aggre- 

 gation ; 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. 



