302 ; G. H. PARKER 
direction and that, while the currents naturally set in through 
the siphonozodids with great freedom, they take the opposite 
course, only under considerable stress as though they were work- 
ing against the natural mechanism of the pore. A close and 
often repeated inspection of the siphonozodids of Renilla when 
in a normal resting state failed to elicit the least evidence of 
natural currents running through these apertures in an outward 
direction. No carmine particles were ever seen wafted out- 
wardly from these zodids and methylen-blue solutions were 
never observed to be swept away from them. Excepting under 
an internal pressure of 5 or more cm. of water, | have never seen 
anything emerge from the siphonozoéid pores. ‘This condition is 
probably associated with the fact, long ago pointed out by Wilson 
(84, p. 18), that in Renilla the siphonozodids are devoid of dor- 
sal mesenteric filaments and hence produce no outward currents, 
their single ciliated organ being a siphonoglyph, by which water 
is earried inward. In many pennatulids the siphonozoéids 
possess dorsal mesenteric filaments (Lightbown, 718) as well as 
siphonoglyphs, and may therefore exhibit exhalent as well as 
inhalent activities. This condition probably explains the differ- 
ence between my observations and those of Musgrave (’09, p. 
455), who found in the siphonozoéids of Pennatula good evi- 
dence for excurrent as well as incurrent action, whereas in Renilla 
I found no trace of excurrents whatever. My observations com- 
pletely confirm Wilson’s statement (’83, p. 725) that the siphono- 
zooids of Renilla are the chief inhalent apertures for the colony. 
The axial stphonozodid 
This large zoédid in the chief axis of the Renilla colony and near 
the center of its rachis was shown Miiller (’64, p. 345) by his little 
daughter, who saw a jet of water spurt out of it when she picked 
up a living Renilla from the sea. This observation can be con- 
firmed by anyone to whom living material is available. On tak- 
ing up an inflated specimen, contraction at once occurs and water 
is discharged in the form of a fine jet from the axial siphono- 
zooid. The same form of discharge can be observed in animals 
