26 DROSEKA ROTUNDIFOLfA. CHAP. II. 



many of the other tentacles. We here see clearly that 

 such bodies as particles of cinder or little balls oi 

 paper, after being carried by the tentacles to the 

 central glands, act very differently from fragments of 

 flies, in causing the movement of the surrounding 

 tentacles. 



I made, without carefully recording the times of 

 movement, many similar trials with other substances, 

 such as splinters of white and blue glass, particles of 

 cork, minute bits of gold-leaf, &c. ; and the propor- 

 tional number of cases varied much in which the 

 tentacles reached the centre, or moved only slightly, 

 or not at all. One evening, particles of glass and 

 cork, rather larger than those usually employed, were 

 placed on about a dozen glands, and next morning, 

 after 13 hrs., every single tentacle had carried its little 

 load to the centre ; but the unusually large size of the 

 particles will account for this result. In another case 

 f- of the particles of cinder, glass, and thread, placed 

 on separate glands, were carried towards, or actually 

 to, the centre ; in another case --, in another -jV, and 

 in the last case only -^ were thus carried inwards, the 

 small proportion being here clue, at least in part, to the 

 leaves being rather old and inactive. Occasionally a 

 gland, with its light load, could be seen through a 

 strong lens to move an extremely short distance and 

 then stop ; this was especially apt to occur when ex- 

 cessively minute particles, much less than those of 

 which the measurements will be immediately given, 

 were placed on glands ; so that we here have nearly 

 the limit of any action. 



I was so much surprised at the smallness of the par- 

 ticles which caused the tentacles to become greatly 

 inflected that it seemed worth while carefully to 

 ascertain how minute a particle would plainly act. 



