Chap. X. DIEECTION OF INFLECTED TENTACLES. 243 



that is, if tlie stimulus has been sufficient and not 

 injurious. Now, when the glands of the disc are 

 excited, the exterior tentacles are affected in exactly 

 the same manner : the aggregation always com- 

 mences in their glands, though these have not been 

 directly excited, but have only received some influ- 

 ence from the disc, as shown by their increased acid 

 secretion. The protoplasm within the cells immedi- 

 ately beneath the glands are next affected, and so 

 downwards from cell to cell to the bases of the 

 tentacles. This process apparently deserves to be 

 called a reflex action, in the same manner as when a 

 sensory nerve is irritated, and carries an impression 

 to a ganglion which sends back some influence to a 

 muscle or gland, causing movement or increased 

 secretion ; but the action in the two cases is probably 

 of a widely different nature. After the protoplasm in a 

 tentacle has been aggregated, its redissolution always 

 begins in the lower part, and slowly travels up the 

 pedicel to the gland, so that the protopla'sm last 

 aggregated is first redissolved. This probably depends 

 merely on the protoplasm being less and less aggre- 

 gated, lower and lower down in the tentacles, as can 

 be seen plainly when the excitement has been slight. 

 As soon, therefore, as the aggregating action altogether 

 ceases, redissolution naturally commences in the less 

 strongly aggregated matter in the lowest part of the 

 tentacle, and is there first completed. 



Direction of the Inflected Tentacles. — When a particle 

 of any kind is placed on the gland of one of the outer 

 tentacles, this invariably moves towards the centre of 

 the leaf; and so it is with all. the tentacles of a leaf 

 immersed in any exciting fluid. The glands of the 

 exterior tentacles then form a ring round the middle 

 part of the disc, as shown in a previous figure (fig. 4. 



