356 G. H. PARKER 
Although it may be possible that there are individual differ- 
ences in Renilla and that some specimens possess terminal 
peduncle pores and others do not, it seems to me more probable 
that such pores are characteristically present and that they open 
normally only under considerable internal pressure such as is 
represented by a column of sea-water approximately a meter in 
height—a pressure that may at. times rupture the wall of the 
peduncle laterally rather than force open the pore. 
Aside from the discharge of sea-water under unusual pressure, 
I have never seen any evidence that the terminal pore of the 
peduncle is an exhalent aperture. In all experiments with 
Renilla in which carmine or methylen blue have been used I 
have never observed anything that led me to suppose that water 
was being discharged from this pore. When a fully inflated 
peduncle on a living Renilla is quickly and completely ligated 
about midway its length and it is thus left distended and still 
attached to the colony, it will retain its inflated condition un- 
changed for hours, though when a small hole is made in it by the 
prick of a pin it collapses at once. I therefore believe it improba- 
ble that the terminal pore of the peduncle serves as an exit for 
water except under very unusual pressure. 
The opinion that it is an inhalent aperture is still more problem- 
atical. I have repeated on Renilla Musgrave’s experiment (’09, 
p. 456) on Pteroides in which the peduncle of this animal was 
immersed in a colored fluid. A deeply colored solution of methy- 
len blue in sea-water was prepared and four narrow-necked flasks 
were filled with it. Into the neck of each flask the-peduncle of 
a Renilla was inserted the rachis of the animal resting on the 
edges of the mouth of the flask. Each flask with its contained 
fluid and Renilla was then cautiously sunk in a vessel of sea-water 
so as to cause as little mingling of the methylen-blue solution and 
the sea-water as possible. After the preparations had been 
standing ten hours the Renillas were removed, rinsed gently, 
and their peduncles examined. ‘The outer surfaces of these parts 
were stained deep blue, but, contrary to the results obtained by 
Musgrave on Pteroides, no blue fluid or blue staining could be 
found inside the peduncles, showing that the terminal pore had 
not served as an inlet. 
