ACTIVITIES OF COLONIAL ANIMALS 359 
canals, two lateral ones in addition to the two characteristic of 
the peduncle. Wilson (’83, p. 726) corroborated all of Eisen’s 
statements except that concerning the presence of the four canals, 
and showed that, although the superior canal of the peduncle 
communicated directly with the pore of the axial siphonozodid, 
it was also connected with the cavities of the polyps as was the 
inferior canal. Much of this freedom of internal communica- 
tion was demonstrated through injection by Musgrave (’09, p. 
448) in the several sea-pens investigated by her. 
In Renilla amethystina I studied the system of internal canals 
chiefly by means of injections. ‘Two types of injecting fluids 
were used: first, solutions such as methylen blue in sea-water 
and, second, finely divided solids such as india ink in sea-water. 
The first kind would naturally pass through very minute aper- 
tures, the second only through those of a larger size. The in- 
jecting was accomplished under the pressure of a column of 
water, 10 to 15 em. of which was usually found to be sufficient to 
drive the fluid forward. 
If the peduncle of a Renilla is cut off close to its attachment 
to the rachis and the cannula of the injection tube tied firmly into 
the superior canal, the inferior canal being slit open throughout 
most of its length, it requires only a few centimeters of pressure 
to drive either a methylen-blue solution or an india-ink suspen- 
sion down the length of the superior canal and through the num- 
erous apertures of the septum between the two canals into the 
open inferior canal. 
If, now, an additional ligature is applied to such a preparation 
at a point about one-quarter of the length of the peduncle from 
its tip, thus excluding this distal quarter from participating in 
the flow of the injection fluid, the fluid not only fills the remainder 
of the superior canal, but also flows over into the inferior one. 
On applying a third ligature to the peduncle about midway its 
length, it was found that, though the superior canal filled, neither 
the methylen-blue solution nor the india-ink suspension passed 
-into the inferior canal. Hence it must be concluded that the 
pores in the peduncular septum by which the superior canal com- 
municates with the inferior must be limited to about the distal 
