122 



BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



a separate lateral branch of the stolon. These lateral branches, the 

 individual pedicels of the zooids, arise at rather close but not very 

 regular intervals all around the stolon and are Somewhat less in 

 length than the body of the zooid they l)ear. The largest zooid 

 (about 4 mm. in greatest diameter) is borne on the extreme tip of the 

 stolon, but. with this exception, the zooids become regularly larger 

 and more mature as the base of the stolon is approached. 



Zooids somewhat egg-shaped, slightly compressed laterally, the 

 pedicel arising from the small end, which is the posterior ventral 

 part of the body. Apertures but slightly prominent, the branchial 

 near the dorsal side of the large end of the body; the atrial nearly 

 opposite the origin of the pedicel. Both are lobed, but the lobes are 

 not readily counted in the contracted preserved specimen. Nine 



Figs. 77, 78. — Perophora hutchisoni MacDonald. 77, Part of a colony. X 1.25. 



78, Zooid. X 13. 



branchial and seven atrial lobes were demonstrated in one individual. 

 Stolon, pedicels, and zooids are insheathed in a layer of clear color- 

 less test substance, which becomes thicker on that part of the body of 

 the zooid where the pedicel arises so that the outline of the zooid 

 tapers off into that of the pedicel. Yellowish brown corpuscles occur 

 in branching vessels in the mantel, digestive organs, and to some 

 extent in other parts of the body. 



Mantle musculature slight, composed of delicate, widely spaced 

 bands. Some of these surround the apertures, others extend pos- 

 teriorly on the sides from about the branchial aperture, or obliquely 

 backward from the region of the endostyle. 



Tentacles about 30 in number. Three orders can be recognized, but 

 there is often considerable inequality in their arrangement, especially 

 as far as the smaller tentacles are concerned. These are inserted a 

 little nearer the aperture than the large ones. 



Dorsal languets small, inserted on the median dorsal vessel. 



