208 ANNUAL REPORT 



even those not in actual contact with the prisoner. This fluid 

 is quite abundant, looking like drops, if the closed halves are 

 forcibly separated. It surrounds the enclosed object and soon 

 dissolves the same. If finished, the secretion is absorbed, and 

 with it the digested food; the glands become dry, and the halves 

 of the leaf open again for another victim. Of the caught object 

 everything that could be consumed has disappeared. The six 

 bristles, which in the closed cavity were bent like the blades of 

 a knife, again assume their former position. 



The length of time needed for digestion varies according to 

 the size of the victim. Usually the halves remain closed from 

 eight to fourteen, even twenty days. Larger articulates, such as 

 centipedes, can escape, if their whole body is not enclosed, by 

 mere strength, since the margins and teeth of the halves are 

 somewhat flexible; smaller animals are always lost, and they soon 

 suffocate in the fluid covering them. 



The whole trap, although similar to that of the Sundew, is 

 quite an improvement of it, and the division of labor is much 

 more pronounced, as the six spikes are not used both as organs 

 of sensation and digestion, but only for the former purpose. 

 The outer long and pointed teeth are also free from glands, and 

 simply serve to enclose the victims more securely. We have 

 therefore in the traps of the Dlonwa organs for three distinct 

 functions: to excite, to catch and to digest, whilst in the Drosera 

 the same functions are performed by organs of one kind. The 

 transmission of an excitement is also much more rapid in our 

 Venus fly-trap. 



We have already compared this transmission with the similar 

 one in the organism of animals. But strange to say even elec- 

 trical currents have been observed in the Venus fly-trap, which 

 prove that it has the greatest analogy with muscles and nerves 

 even in this respect. A current of positive electricity flows from 

 the base to the extreme end of the trap, another negative one 

 can be observed in the leaf stem, and as seat of the source of this 

 electricity the upper layers of cells of the surface of the trap 

 and the middle rib have been ascertained. Every excitement of 

 the leaf changes at once the intensity of the electric current, 

 and as this change produces a movement of the halves compris- 

 ing the trap we may assume that the electric current regulates 

 the opening and closing of the whole trap. 



The 2i\\ied Aldrovandia (Fig. 13) — allied Jas far as the struc- 

 ture of the trap is concerned — is an aquatic plant, found in 



