38 



UNITED STATES NATIONAL MUSEUM BULLETIN 251 



some zooids of a colony from the Palau Islands, postabdomen issues 

 from left posterior side of intestinal loop (fig. 8b) just at level of 

 junction between hind stomach and middle intestine, instead of ex- 

 tending from rear end of loop. 



Branchial aperture 6-lobed; each lobe may be subdivided into 3 

 lobules in some specimens. Atrial aperature opening at rather a 

 higher level, varying from first transverse vessel to fourth stigmatal 

 row ; roundish or oval in outline. Atrial languet usually short, even 

 indistinct in some specimens, tip usually simple or rarely trifid ; situa- 

 tion of languet varies from posterior side of dorsal ganglion to anterior 

 side of atrial aperture. About 15 longitudinal muscles on each side of 

 thorax, several ventral ones of which are running obliquely or partially 

 transversely. Stigmatal rows 7 to 10 ; number of stigmata in each row 

 fewer in smaller zooids of the colonies from the Gilbert Islands, only 

 about 10 ; may number up to 30 in larger zooids of colonies from the 

 Palau Islands. In the latter case, about 6 stigmata near ea€h end of 

 respective rows diminish in size toward endostyle or dorsomedian line. 

 Stigmata fringed with yellowish corpuscles in some specimens. 

 Transverse vessels heavily pigmented in some zooids; horizontal 

 membranes well developed, but without papillae. Some larger zooids 

 of the 15 mm. X 12 mm. colony from the Palau Islands are provided 

 with some fine transverse vessels, just like parastigmatic vessels, par- 

 tially on the outer side of the stigmatal row. Tentacles 8 to 12, larger 

 and smaller ones alternating regularly ; situated anteriorly far apart 

 from the peripharyngeal band and somewhat triangular in shape in 

 some zooids examined. Ciliated groove a small oval opening; dorsal 

 languets finger-shaped and displaced from the dorsomedian line to the 

 left side for the distance of 2 to 5 stigmata. Anus opening at level of 



Figure 9. — Amaroucium multiplicatum (Shiitcr): a, right side of fully developed embryo 

 from same colony as thai of figure 8f; b, right side of slightly younger embryo from same 

 colony; c, right side of embryo from the Palau Islands; d, one of the attachment discs. 



