316 DARWmiANA. 



not last long; the particles of "aggregated proto- 

 plasm " redissolve, tlie process of redissolution travel- 

 ing upward from tlie base of the tentacle to the gland 

 in a reverse direction to that of the .aggregation. 

 Whenever the action is more prolonged or intense, as 

 when a bit of meat or crushed fly,' or a fitting solu- 

 tion, is left upon the gland, the aggregation proceeds 

 further, so that the whole protoplasm of each cell con- 

 denses into one or two masses, or into a single mass 

 which will often separate into two, which afterward 

 reunite ; indeed, they incessantly change their forms 

 and positions, being never at rest, although their 

 movements are rather slow. In appearance and move- 

 ments they are very like amoebae and the white cor- 

 puscles of the blood. Their motion, along with the 

 streaming movement of rotation in the layer of white 

 granular protoplasm that flows along the walls of the 

 cell, under the high powers of the microscope " pre 

 sents a wonderful scene of vital activity." This con- 

 tinues while the tentacle is inflected or the gland fed 

 by animal matter, but vanishes by dissolution when 

 the work is over and the tentacle straightens. That, 

 absoi'ption takes place, and matter is conveyed from 

 cell to cell, is well made out, especially by the exper- 

 iments with carbonate of ammonia. ^N^evertheless, 

 this aggregation is not dependent upon absorption, for 

 it equally occurs from mechanical irritation of the 

 gland, and always accompanies inflection, however 

 caused, though it may take place without it. This is 

 also apparent from the astonishingly minute quantity 

 of certain substances which sufiices to produce sensible 

 inflection and aggregation — such, for instance, as the 



