484 G. H. PARKER 
show rachidial waves. In the band a wave will ordinarily start 
from each end, the two waves meeting and becoming obliterated 
near the center, which is really the apical margin. ‘The central 
portion of a rachis from which the edge has been trimmed will 
exhibit symmetrical waves like those of a small rachis. If the 
central part of the rachis is reduced by a delamination of the edge 
till an area containing only a few zodids results, this small cen- 
tral area will pulse, though it is almost impossible to distinguish 
any special direction to its movements. If a preparation is 
made by cutting off the sides of the rachis and leaving the axis 
of that part attached to the peduncle, the rachidial wave, when 
it appears, can be followed from a point close to the distal end 
of the peduncle over the whole length of that part as well as over 
TABLE 2 
Intervals in seconds between rachidial waves on the separated right and left halves 
of a rachis 
NUMBER OF WAVE 
AVERAGES 
1 2 3 4 5 6 7 8 4) 10 
Right half....| 105 | 115 | 110 | 125 | 120 | 125 | 120 | 115 | 110 | 115 |) 115.0 
Left half.....| 105 | 125 | 110 | 180 | 115 | 125 | 110 | 115 | 105 | 120} 116.0 
the axis of the rachis to the region of its disappearance on the 
natural margin. 
As might be inferred from the experiments described in the 
preceding paragraphs, any fair-sized fragment of the rachis of 
Renilla may exhibit rachidial peristalsis. Thus if a rachis is 
cut in two lengthwise through its chief axis, the two symmetrical 
halves will continue to show a rachidial peristalsis in which the 
waves of the two pieces, notwithstanding their separation, run 
at very nearly the same rate, as shown in table 2. If the two 
halves come from a Renilla that is already in rachidial peristalsis 
and the longitudinal cut is made quickly, the peristalsis is ordi- 
narily. not interfered with. After such an operation the two 
resulting halves not only beat at the same rate, but their waves 
even keep in phase for a considerable period of time. Of course 
sooner or later this agreement disappears. 
