Cuar. X.] TRANSMISSION OF MOTOR IMPULSE. 191 
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 neighbouring 
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 toa 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, 
Lhave seen movement in ten seconds, and repeatedly within a 
minute; but a much larger bit placed on several lands on 
the disc does not cause the exterior tentacles to bend until 
half an hour or even several hours have elapsed. 
The motor impulse spreads gradually on all sides from one 
or more excited glands, so that the tentacles which stand 
nearest are always first affected. Hence, when the glands. 
in the centre of the disc are excited, the extreme marginal 
tentacles are the last inflected. But the glands on different 
parts of the leaf transmit their motor power in a somewhat 
different manner. Ifa bit of meat be placed on the long- 
headed gland of a marginal tentacle, it quickly transmits 
an impulse to its own bending portion; but never, as far as 
I have observed, to the adjoining tentacles ; for these are not 
affected until the meat has been carried to the central glands, 
which then radiate forth their conjoint impulse on all sides. 
On four occasions leaves were prepared by removing some 
days previously all the glands from the centre, so that these 
could not be excited by the bits of meat brought to them by 
the inflection of the marginal tentacles; and now these 
marginal tentacles re-expanded after a time without any 
other tentacle being affected. Other leaves were similarly 
prepared, and bits of meat were placed on the glands of two. 
tentacles in the third row from the outside, and on the glands. 
of two tentacles in the fifth row. In these four cases the. 
impulse was sent in the first place laterally, that is, in the 
same concentric row of tentacles, and then towards the 
centre; but not centrifugally, or towards the exterior 
tentacles. In one of these cases only a single tentacle on 
each side of the one with meat was affected. In the three: 
