EXPERIMENTAL OBSERV'ATIONS OX” PENX^ATULIDS. 473 
Pennatnlids it seems extremely probable that the 
main impetus of the circulating circuit has its 
origin in the stalk. 
The Powers op Locomotion. 
It is generally assumed that the usual position of a liviug- 
Pennatulid is an erect one with the stalk buried in the mud 
of the sea bottom. Such is undoubtedly the case with forms 
inhabiting shallow water like Virgularia, but we have 
reason to believe from records of observation by early writers 
(Bohadsch, Ellis, etc.) and from a study of the general 
anatomy of the Pennatnlids, that the stationary erect con- 
dition is not necessarily alwa 3 ’s maintained. 
It is extremely probable that many deep-sea Pennatnlids 
are endowed with certain controlled powers of locomotion, 
and may transfer themselves from place to place under suit- 
able conditions. 
In Pterccides, for example, the protraction of the 
“oblique musculature” of the axis would enable the stalk 
with a spiral twist to bore into the sand or mud of the sea 
bottom in true screw-like fashion, when the bulb-like dilata- 
tion of the base would assist in supporting the colony in 
a vertical position. In this erect position the basal pores 
of the stalk (fig. 3) would, it is assumed, remain closed and 
inactive, and the circulatoiy current would now be dependent 
upon the activity of the autozooids, siphonozooids, and dorsal 
pore.s, for in this position the remaining portion of the colon)" 
must necessarily remain more or less quiescent, for it is 
obvious that any activity on the part of the muscles would 
dislodge it from its basal burrow. 
The retraction of the oblique musculature with the co- 
operative activit)" of the apical and sphincter muscles, com- 
bined with the peristaltic action of the musculature of the 
body-wall Avould not only Avithdraw the colony from its 
basal support, but propel it Avith such considerable force 
through the Avater as. to accomplish a swimming excursion 
of no small maguitude. These muscular movements Avhich 
