1880. ] The Siphonophores. 625 
resembling in that»respect the necto-calyxes, and are so closely 
approximated, as to overlap each other and apparently to form 
a single unjointed prism. They have an irregular triangular out- 
line, and a flat leaf-like shape. In Agalma they seem to serve 
simply the function of protecting the structure beneath them. 
They are traversed throughout by a medially placed canal or 
tube, which terminates blindly at the distal end, and opens at the 
other extremity into the cavity of the stem. The junction with 
the stem is by means of a pedicel, which is appended to one angle 
of the bract and has muscular fibers on its under side. ; 
At the very tip of the cov- 
ering scale there is a cluster 
of cells which have been sup- 
posed to indicate the homolo- 
gies of the scale with a por- 
tion of the necto-calyx. These 
cells are looked upon as 
rudimentary tentacles, and 
are relatively much larger in 
the young scale than in the 
adult. 
Agalma has, in addition to 
those described, two kinds of 
covering scales, which are 
embryonic and provisional. 
These will be mentioned un- 
der the embryology, for they 
are confined to early stages in 
the development of the animal, 
The feeding polyps which lie under the covering scales and 
-Which are protected by these modified medusa bells, next claim a 
description. They are known as the polypites. 
d. Polypites.—Certain flask-shaped bodies, more highly colored 
than those yet described, are appended to the polyp-stem, and 
their distal extremities extend out between the covering scales. — 
‘hey are supposed to be stomachs and to eat for the whole col- 
Ony. A mouth at one end takes the food, hepatic cells arranged 
iN rows along the inside of the polyp assist to digest it, and after 
being digested the nutritive fluid is passed into the stem cavity 
through which it is distributed to every member of the community. 
From the base of the polypite on the upper side arise the tentacle 
Fic. 3.—Covering scale. 
