ACTIVITIES OF COLONIAL ANIMALS 505 
paralleling in all respects what has been found for the transmis- 
sion of phosphorescent impulses. 
The rate at which the impulse to zodid contraction traverses 
the rachis can be measured in much the same way as that for 
phosphorescent transmisson. When a band of tissue is cut from 
the edge of a large rachis, pinned out in sea-water, and allowed to 
remain undisturbed till its zodids have expanded, a stimulus 
applied at one end is followed by a wave of contraction that 
starts among the zodids at the stimulated end and progresses 
to those at the opposite end. Although on the uncut rachis 
TABLE 7 
Times in seconds for the passage of waves of zo6id contraction over strips of Renilla 
rachis. The stimulus, pressure of a rod, was applied first at the right-hand end 
of the preparation and then at the left-hand end. The preparations were the same 
as those used in the determinations given in table 4. Temperature of water, 21°C. 
NUMBERS OF THE TESTS 
1 2 3 4 5 6 7 8 9 10 
cm. 
A SO] Ae IL Oo eA NEO) eA | ak E Sa O) Nica cee ali a ap 1.14 9.3 
B Tem) ALECO Wa COC a, |p eee Sa aC Lee? ft Da Sy at i tb 24 Fl 1.20 9.2 
G TE TEE PU LPF | TL eae ae OM a eT SPL) 16 9.3 
D ee le eA Olea ON ele 2a bea. tO) a2 1.18 9.2 
E WA thea aba |e tbetball MEO MPAs). eb, ae bali heals hea 1.24 9.2 
(Cemenal aera esta y ety src e kee Pee RB Sone elec ick hs. oc SiahS sycpalmcbar’ 1.18 9.24 
such waves can scarcely be seen, their presence can be demon- 
strated beyond a doubt when a long stretch of tissue, such as the 
band described, is used, and if the interval beween the contrac- 
tion of the first large zodid on the stimulated end and that of the 
last large one on the opposite end is timed, the rate of trans- 
mission of the impulse to zoéid contraction can be easily found. 
The five bands that were used for the determination of the 
rates of the phosphorescent impulses on the night of August 15th 
were used again the next morning in daylight for the determina- 
tion of the rates for zodid contraction. The results are given 
in table 7, and it will be seen that the average rate for these five 
pieces is 9.24 em. in 1.18 second, or 7.83 em. per second. This 
