472 
EDITH M. MUSGRAYE. 
In extremely larg’e and robust Pennatulids such means are 
apparently insufficient for that purpose. In Anthoptilum 
grandiflorum (fig’s. 10 and 11) we find a modification of the 
upper portion of the stalk in preserved specimens in the form 
of a thickened and much-folded zone, caused by an extra- 
ordinary development of the distensile spongy tissue and 
transverse musculature of the body-wall. This region is 
also chai’acterised by the unusual presence of numerous 
siphonozooids (fig. 10, si.). 
This structural modification doubtless serv'es as a powerful 
pumping apparatus for the institution and maintenance of 
currents tohigher altitudesand more distant partsof thecolony. 
An intermediate condition between the small species of 
Pennatula(P. rubra and P. phosphorea) and the magni- 
ficent species Anthoptilum grandiflorum is indicated in 
the comparatively large species of Penuatula (P. naresi 
and P. borealis). In these forms a slight protuberance of 
the body-wall occurs in the region of the thickened zone, 
and in this instance also is due to an increased growth, but 
to a less degree than in Anthoptilum of the distensile 
spong-y tissue and transverse musculature of the body-wall. 
In Pteroeides structural modifications of the stalk, to serve 
the same purpose but undoubtedly with greater efficiency, has 
proceeded still further. This genus is characterised by the 
development in the stalk of an extremely powerful sphincter 
muscle (fig. 14), whose pmnp-like actions, co-operated with 
those of the powerfully built “ oblique musculature ” of the 
stalk and the musculature of the body- wall are apparently 
necessary to institute and complete the circulation of fluids 
within the large, densely built, and compact colony. 
We have incontrovertible evidence of the distensile function 
of autozooids and siphonozooids in inducing inhalent and 
exhalent currents in tlie region of the rachis, and we have 
also experimental evidence of the function of the four dorsal 
pores for exhalent, and probably also for inhalent, purposes 
(figs. 5 and G), but from the evidence based upon a study 
of the musculature in connection with the canal systems of 
