258 DEOSEEA ROTUNDIFOLIA. CHAP. X, 



though rejected by most others, is that the whole cell, 

 including the walls, actively contracts. If the walls are 

 composed solely of non-nitrogenous cellulose, this view 

 is highly improbable ; but it can hardly be doubted 

 that they must be permeated by proteid matter, at 

 least whilst they are growing. Nor does there seem 

 any inherent improbability in the cell-walls of Drosera 

 contracting, considering their high state of organisa- 

 tion ; as shown in the case of the glands by their power 

 of absorption and secretion, and by being exquisitely 

 sensitive so as to be affected by the pressure of the 

 most minute particles. The cell-walls of the pedicels 

 also allow various impulses to pass through them, 

 inducing movement, increased secretion and aggrega- 

 tion. On the whole the belief that the walls of certain 

 cells contract, some of their contained fluid being at 

 the same time forced outwards, perhaps accords best 

 with the observed facts. If this view is rejected, the 

 next most probable one is that the fluid contents of 

 the cells shrink, owing to a change in their molecular 

 state, with the consequent closing in of the walls. 

 Anyhow, the movement can hardly be attributed to 

 the elasticity of the walls, together with a previous 

 state of tension. 



With respect to the nature of the motor impulse 

 which is transmitted from the glands down the pedi- 

 cels and across the disc, it seems not improbable that 

 it is closely allied to that influence which causes the 

 protoplasm within the cells of the glands and ten- 

 tacles to aggregate. We have seen that both forces 

 originate in and proceed from the glands within a 

 few seconds of the same time, and are excited by the 

 same causes. The aggregation of the protoplasm last? 

 almost as long as the tentacles remain inflected, 

 even though this be for more than a week ; but the 



