ACTIVITIES OF COLONIAL ANIMALS Bor 
Six specimens of Renilla were allowed to discharge their con- 
tained water, and their peduncles were firmly ligated at about 
midlength. Thus the distal half of the peduncle, though still 
connected with the rest of the colony by its wall, had its communi- 
cation with the colony by its canals cut off. These specimens 
were then returned to sea-water to determine whether the dis- 
tal portions of the peduncles could refill themselves. After 
twelve hours they were as unfilled as at the beginning of the ex- 
periment. After twenty-four hours two of the six had filled, but 
on cutting these from the colony in the region just proximal to 
that at which they were tied, they quickly emptied themselves 
by discharging their fluid contents at the cut end, showing that 
in these two instances the ligatures had failed to hold. In the 
four empty peduncles no such looseness was observable. This 
experiment was repeated on another set of ten animals and with 
similar results. For some time none of the peduncles filled, but 
after thirty hours three of them were found distended, and in all 
of these the ligatures had loosened. Apparently the peduncle, 
which is a highly muscular tube, is extremely difficult to ligate 
under water and by its continued activity eventually shghtly 
loosens ligatures that under ordinary circumstances would have 
held. 
- The results of the experiments in ligating peduncles and in 
sinking them into colored fluid, in both of which the peduncles 
failed to fill themselves from the outside, lead to the conclusion 
that the terminal pore of that structure is not to be regarded as 
an inlet for sea-water. This conclusion accords with the fact 
that a Renilla immediately after its peduncle has been firmly 
ligated will fill itself with sea-water long before the ligature 
could have worked loose even to a small degree. Although I 
am convinced that the peduncle of Renilla possesses a terminal 
pore, I do not believe that it possesses inhalent and exhalent 
functions such as have been found by Musgrave (’09, p. 471) for 
the corresponding openings in other sea-pens. In Renilla, so 
far as I can judge, the terminal pore is at best an outlet opening 
serviceable only under excessive pressure. 
