CHAP. HI. THE PROCESS OF AGGREGATION. 55 



218, of water), the tentacles are paralysed, and do not 

 become inflected, yet they soon exhibit strongly 

 marked aggregation. Moreover, the short central 

 tentacles of a leaf which has been immersed in a 

 weak solution of any salt of ammonia, or in any 

 nitrogenous organic fluid, do not become in the least 

 inflected; nevertheless they exhibit all the pheno- 

 mena of aggregation. On the other hand, several 

 acids cause strongly pronounced inflection, but no 

 aggregation. 



It is an important fact that when an organic or in- 

 organic object is placed on the glands of the disc, 

 and the exterior tentacles are thus caused to bend 

 inwards, not only is the secretion from the glands of 

 the latter increased in quantity and rendered acid, 

 but the contents of the cells of their pedicels become 

 aggregated. The process always commences in the 

 glands, although these have not as yet touched any 

 object. Some force or influence must, therefore, be 

 transmitted from the central glands to the exterior 

 tentacles, first to near their bases causing this part to 

 bend, and next to the glands causing them to secrete 

 more copiously. After a short time the glands, thus 

 indirectly excited, transmit or reflect some influence 

 down their own pedicels, inducing aggregation in cell 

 beneath cell to their bases. 



It seems at first sight a probable view that aggrega- 

 tion is due to the glands being excited to secrete more 

 copiously, so that sufficient fluid is not left in their 

 cells, and in the cells of the pedicels, to hold the 

 protoplasm in solution. In favour of this view is the 

 fact that aggregation follows the inflection of the 

 tentacles, and during the movement the glands gener- 

 ally* or, as I believe, always, secrete more copiously 

 than they did before. Again, during the re-expansion 



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