464 
EDITH M. HUSGEAVE. 
Structural Modifications in the Stalk. 
Several extremely large and robust specimens of Autbo- 
ptilum grandiflorum present a peculiar modification of 
the upper portion of the stalk in the form of a curiously 
folded and thickened, ring-like zone (fig. 10, T.Z.). This was 
found upon internal investigation to be caused by an extra- 
ordinary growth of the spongy tissue in this region (fig. 11, 
L.M.P.) in the form of numerous laminate vertical processes 
with free edges directed inwards, and lined internally by 
a moderately well-defined musculature comparable to the 
transverse musculature of the body-wall in other forms, but 
in this instance produced into the folds and convolutions 
caused by the remarkable development of the spongy tissue. 
The laininm are traversed by numerous canals, Avhich 
ramify within their substance and communicate by numerous 
apertui'es with the interlaminate interstices of the body 
cavity. 
It was unfortunate that the state of preservation of the 
specimens would not permit a detailed investigation of the 
histology of the lamime, but a microscopic study of the body- 
wall in the lower region of the thickened zone proved of 
great interest. Its outer surface was observed to be studded 
with numerous minute papillae, which proved upon examina- 
tion to be siphon ozooids (fig. 10, si .) — extremely small, but 
of the normal Peniiatulid type, with mouth apertures and the 
usual number of mesenteries. Their coelentera communicate 
as in other forms with the large central canals by means of 
the connecting canals of the spongy tissue. 
The curiously folded epithelium of the outer body-wall, and 
also that of the siphonozooids, contained numerous deeply 
staining gland cells from which a mucus-like secretion was 
seen exuding in considerable quantity. 
The occurrence of siphonozooids^ in this unusual region 
' The presence of siphonozooids in the stalk of Pennatulids is not 
quite unique, for Hickson (1907, p. 1.3) has also observed them in the 
stalk of “Unihellula carpenter!. ” 
