23-1 DKOSERA ROTUNDIFOLIA. CIIAF. X. 



glands, and only a few of the immediately surround- 

 ing short tentacles are inflected ; place it on several 

 glands, and many more are acted on; place it on 

 thirty or forty, and all the tentacles, including the 

 extreme marginal ones, become closely inflected. We 

 thus see that the impulses proceeding from a number 

 of glands strengthen one another, spread farther, and 

 act on a larger number of tentacles, than the im- 

 pulse from any single gland. 



Transmission of the Motor Impulse. In every case 

 the impulse from a gland has to travel for at least 

 a short distance to the basal part of the tentacle, 

 the upper part and the gland itself being merely 

 carried by the inflection of the lower part. The 

 impulse is thus always transmitted down nearly 

 the whole length of the pedicel. When the central 

 glands are stimulated, and the extreme marginal ten- 

 tacles become inflected, the impulse is transmitted 

 across half the diameter of the disc ; and when the 

 glands on one side of the disc are stimulated, the 

 impulse is transmitted across nearly the whole width 

 of the disc. A gland transmits its motor impulse 

 far more easily and quickly down its own tentacle 

 to the bending place than across the disc to neigh- 

 bouring tentacles. Thus a minute dose of a very 

 weak solution of ammonia, if given to one of the 

 glands of the exterior tentacles, causes it to bend and 

 reach the centre; whereas a large drop of the same 

 solution, given to a score of glands on the disc, will 

 not cause through their combined influence the least 

 inflection of the exterior tentacles. Again, when a 

 bit of meat is placed on the gland of an exterior 

 tentacle, I have seen movement in ten seconds, and 

 repeatedly within a minute; but a much larger bit 

 placed on several glands on the disc does not causa 



