EXPERIMENTAL OBSERVATIONS ON PENNATULTDS. 479 
(M.F.), which probably play an important part in the expansion and 
contraction of the canals. Many of the endodernial cells also contain 
ingested particles of the injected carmine, which have Ijeen conveyed to 
this 2 )ortion of the colony by means of the circulating currents. The 
presence of carmine in the cells may indicate their possession of 
nutritive and excretory functions. The mucous secretion from the cells, 
which is no doubt responsible for the viscid character of the contents 
of the canals, may be lubricating in function, and may from its hygro- 
scopic nature play an important part in the dilatation and contraction 
of the colony. 
PLATE 27. 
Figs. 10-15. 
Fig. 10. — Anthoptilum grandiflorum. Drawing of the ventral 
surface of the stalk to show the folded thickened zone {I’.Z.), princi^^ally 
due in this instance to an extraordinary growth of the spongy (disten- 
sible) tissue composing the internal body-wall, and not to the special 
development of an internal sphincter muscle as in Pte roe ides (fig. 14, 
Spli.M.). Both modifications of structure doubtless serve the same 
function in bringing about the dilatations and contractions of the 
colony. The lower portion of the thickened zone and the region imme- 
diately inferior to it is studded with numerous minute siphonozooids 
(Si.), which play an important part in maintaining the hydrostatic 
equililn'ium of the colony. (Natural size.) 
Fig. 1 1.— Anthopti him grandiflorum. Dissection of the stalk 
from the ventral surface (two thirds natural size), showing the hook-like 
termination of the axis induced by the contraction of tlie muscular 
apparatus controlling it (M.A.A.), the terminal basal aperture of the 
dorsal canal (B.D.Ap.), and the thickened zone (T.Z.) in tlie upper 
portion of the stalk — composed of hydrostatic and muscular spongy 
tissue, which is produced into laminate processes (L.M.P.) presenting a 
free edge to the body-cavity. The outer surface of the thickened zone 
was observed, on microscopical examination, to be studded witli minute 
siphonozooids of the normal Pennatulid type (fig. lU). This extra- 
ordinary development of the laminate processes appears to be unique 
and has not been (observed in any other genus. 
Fig. 12. — Virgularia juncea. Dissection of the stalk from the 
dorsal surface exposing the lumen of the dorsal canal (three quarters 
natural size). The stalk in this genus is characterised by its unusual 
length, tenuity, brittleness and extreme powers of contractility. In 
elemental constitution it is similar to Penna tula (fig. 13) differing only 
from that genus in proportionate development. As in Penna tula the 
muscular body-wall becomes attenuated towards the base, where it 
