470 
EDITH M. MUSGRAVE. 
porting the oblique musculature of the stalk Pteroeides 
appears to be unique. 
The “oblique musculature” of the stalk is present 
in all the forms examined, but its development varies con- 
siderably among the members of the family. It is more 
powerfully developed in Pteroeides than in any other genus 
(fig. 14, and apparently most feebly developed in Pennatula 
phosphorea. The specimens of Anthoptilum grandi- 
florum, Virgularia juncea, and Pennatula rubra 
(figs. 11, 12, 13) in which the oblique musculature is very 
similar, iudicate an intermediate condition between these two 
extreme forms. 
The “sphincter muscle,” so prouounced a feature in 
the stalk of Pteroeides and the well-marked “muscle-bands” 
(fig. 14, and M.B.) are absent in the other forms, but 
ill Virgularia the oblique muscle-fibres gradually assume 
a horizontal inclination as they ascend the stalk (hg. 12, 
M.A.A.). While the chief function of the oblique musculature 
of the stalk appears to be that of supporting and controlling 
the movements of the inferior and basal portion of the axis, 
its protraction and retraction would apparently have a 
manifold purpose. 
With the co-operated action of the longitudinal muscles of 
the body-wall, the protraction of the oblique muscles would 
straighten out the hooked ends until the axis assumed a 
vertical position, and the length of the stalk would thereby 
be increased. 
The oblique action of these muscles, simultaneously assisted 
by the ringed transverse musculature of the body-wall, would 
also increase the diameter of the stalk. 
The extension of the stalk in length and diameter thus 
accomplished would be accompanied by extensions in the 
same direction of the four large central canals, whose fluid 
capacity would thereby be considerably increased. To main- 
tain the internal equilibrium of the colony an inhalent current 
would therefore be induced through the basal pores of the 
stalk so as to fill to distension the large central canals of the 
