148 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



The type and only certain specimen (No. 27) (Cat. No. 6040, 

 U.S.N.M) is from station D5137 (near Jolo Light, Feb. 14, 1908, 

 20 fathoms, sand and shells). Another small colony (No. 68) (Cat. 

 No. 5926, U.S.N.M.) in the collection may be of this species, though 

 the specimen is insufficient to be the basis of a certain conclusion. 

 The differences which it exhibits may be due to age or different con- 

 ditions of growth or different degree and manner of contraction 

 in preservi ttion. The colony co sists of several minute lobes. This 

 is, however, perhaps due to growing on a branching hydroid or 

 bryozoan instead of on a broad surface. The test is not pigmented, 

 but the tissues of the zooids are dark colored. As compared with 

 the specimen just described the zooids have the branchial orifice with 

 shorter (sometimes scarcely noticable) lobes, the atrial tube longer, 

 and the long muscular process wanting, or at least not conspicuously 

 developed. This latter difference may be more or less dependent 

 en the small and lobed condition of the colony, no such large firm 

 mass of test being present for muscular attachment as in the last- 

 described specimen. Club-shaped vascular processes of the middle 

 region of the zooids are, however, well developed. No reproductive 

 organs could be demonstrated. The specimen is from station D5250 

 (near Linao Point, Gulf of Davao, May 18, 1908, 23 fathoms, coral 

 and sand). 



Genus DIDEMNUM Savigny, 1816. 



[=LeptoeUnum Authors.] 



DIDEMNUM GRANDE (Herdman), 1886. 



Plate 30, figs. 20-23. 



1886. Leptoclinum albidum, var. grande Herdman, Rep. Voy Challenger. 



vol. 14, Tunicata, p. 291, pi. 35, figs. 11-14. 

 1009. Didemnum albidum, var. grande Habtmeyer, Bronn's Tler-reicb, 



vol. 3, suppl., p. 1449. 

 1910. Leptoclinum albidum, var. grande Van Name, Proc. Boston Soc. Nat. 



Hist., vol. 34, p. 374. 



Colony of comparatively thin incrusting form, its shape depend- 

 ing largely on the object on which it grows. Though rarely much 

 exceeding an average thickness of 3 mm., it forms colonies of con- 

 siderable extent, some of the specimens measuring 50 to 60 mm. in 

 greatest diameter. There is also one large colony or group of con- 

 fluent colonies from station 305148 which grew upon a slender 

 branching hydroid, enveloping and binding together its branches in 

 such a way that the ascidian colony has taken the form of a sponge- 

 like mass perforated by canals, clefts, and passages, which must, 

 when entire, have been at least 120 mm. in greatest diameter. It is 

 probable that the peculiarities of this colony are due to the form 



