494 G. H. PARKER 
by mechanical stimulation in either part and will pass thence 
over the connecting bridge of tissue to the other part. If two 
symmetrical transverse cuts are made leaving the two parts con- 
nected by a narrow axial bridge, the luminous waves will pass 
from the peduncular to the apical piece or the reverse with per- 
fect freedom. If the region of stimulation is axial in position, the 
Fig.9 An almost divided Renilla stimulated at S for phosphorescence. The 
luminous waves in the peduncular portion of the rachis are unsymmetrical; in 
the apical part, in consequence of the median position of the bridge, they are 
symmetrical. 
Fig. 10 A Renilla partly divided by two longitudinal slits. When the stimu- 
lus to phosphorescence is applied in a median position (S), the luminous waves 
have a symmetrical course (solid arrows); when it is applied in a lateral position 
(dotted S), the course is unsymmetrical (dotted arrows). 
Fig. 11 A Renilla whose rachis has been cut into a scroll and is somewhat 
unfolded. A stimulus to phosphorescence applied at S is followed by a lumi- 
nous wave that takes the course of the arrows. 
spread of the wave over the stimulated part as well as over the 
unstimulated one is symmetrical with reference to the axis. If 
the region of stimulation is lateral to the axis (fig. 9), the spread 
of the wave is unsymmetrical in the stimulated part, but becomes 
symmetrical on the unstimulated part in consequence of the sym- 
metrical position of the bridge. If the rachis is cut into three 
