Chap.X.] transmission OP MOTOR IMPULSK 197 



ly as the uninjured ones on the same leaves; and an eighth 

 headless tentacle became inflected after three additional 

 days. The meat was removed from one of these leaves, and 

 the surface washed with a little stream of water, and after 

 three days the headless tentacle re-expanded for the second 

 time. These tentacles without glands were, however, in a dif- 

 ferent state from those provided with glands and which had 

 absorbed matter from the meat, for the protoplasm within the 

 cells of the former had undergone far less aggregation. From 

 these experiments with headless tentacles it is certain that 

 the glands do not, so far as the motor impulse is concerned, 

 act in a reflex manner like the nerve-ganglia of animals. 



But there is another action, namely that of aggr^ation, 

 which in certain cases may be called reflex, and it is the 

 only known instance in the vegetable kingdom. We should 

 bear in mind that the process does not depend on the previ- 

 ous bending of the tentacles, as we clearly see when leaves 

 are immersed in certain strong solutions. Nor does it de- 

 pend on increased secretion from the glands, and this is 

 shown by several facts, more especially by the papilla?, which 

 do not secrete, yet undergoing aggregation, if given carbon- 

 ate of ammonia or an infusion of raw meat. When a gland 

 is directly stimulated in any way, as by the pressure of a 

 minute particle of glass, the protoplasm within the cells of 

 the gland first becomes aggregated, then that in the cells 

 immediately beneath the gland, and so lower and lower down 

 the tentacles to their bases; that is, if the 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 aggr^ation always com- 

 mences in their glands, though these have not been directly 

 excited, but have only received some influence from the disc, 

 as shown by their increased acid secretion. The protoplasm 

 within the cells immediately beneath the glands are next af- 

 fected, 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 



