132 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



interior of the branchial sac. These membranes became continuous 

 with the bases of the dorsal languets at the median dorsal vessel. 



Intestinal loop long; stomach oval. Generally it is smooth-walled, 

 but numerous narrow longitudinal streaks of dark pigment, which the 

 writer believes indicate slight plications, can be made out in some 

 zooids. 



Reproductive organs beside the intestinal loop, their ducts accom- 

 panying the ascending part of the intestine. Ovary a small sac 

 containing a large number of small eggs. Testes exceedingly nu- 

 merous, small oval bodies covering up much of the ovary and adja- 

 cent portions of the intestinal loop. In some zooids small tailed 

 larvae are present in the atrial cavity, which is more or less expanded 

 to contain them. 



Colonies not mature and those which appear to have grown under 

 less favorable conditions differ from the above description in many 

 respects. The zooids are always much smaller, not often over half 

 or one-third the above size, and among the specimens in the collection 

 none are so conspicuously pigmented as the large ones above de- 

 scribed. Some show no pigment cells at all; the zooids have, how- 

 ever, more or less of a reddish or pale purplish gray tinge due to 

 diffused color. The test has a similar but paler color and is semi- 

 transparent. The zooids are not so completely separate as in the 

 colony above described, the anterior part of the zooid only has its 

 own sheath of test, the posterior part being imbedded in a common 

 mass of test. Several such common masses, each containing a group 

 of zooids, may be united into a single colony, all arising as lobes or 

 branches of a still larger trunk-like mass of test (fig. 86). 



In very immature colonies, perhaps also in those that have passed 

 through a stage of degeneration and shrinkage and are starting to 

 grow again, the zooids, which are small and numerous and have the 

 branchial sac and other internal organs as yet only imperfectly de- 

 veloped, are completely and often quite deeply buried in a common 

 mass of test, as in ordinary compound ascidians, the colony having a 

 short, thick cylindrical form, attached by one end, or in other cases 

 dividing into several lobes or thick branches. The zooids are con- 

 nected by branching vessels in the basal part of the colonies. Some 

 •of the specimens in this undeveloped condition are quite large (one 

 from station D5164 is about 65 mm. high and nearly 20 mm. in trans- 

 verse diameter), and would, if all the zooids which are developing in 

 them should attain the full size, make very extensive colonies. 



The specimens assigned to this species are all from shallow water 

 {not over 30 fathoms), except one from station D5518, from a depth 

 of 200 fathoms. 



