PACIFIC TUXICATA OF U.S. NATIONAL MUSEUM 



63 



Figure 20. — a-c, Didemnum (Didemnum) candidum (Savigny); a, common cloacal aperture 

 fringed with lobules, Hawaiian colony; b, patterns made by pigmentless areas around 

 branchial apertures, Palau specimen; c, spicule from colony from the Palau Islands, 

 X 1800. d, Dide7?inum {Didemnum) moseleyi (Herdman): colony heavily pigmented 

 dark brown, common cloacal apertures well defined on white hypoabdominal layer, 

 Palau Islands, sta. 134. e, /, Didemnum {Didemnum) moseleyi f. granulatum Tokioka; 

 e, cloacal aperture supported by riblike structures made of spicules;/, spicule from colony 

 from sta. 220, X 1800. 



Galapagos Islands were examined. The largest specimen in (lie collec- 

 tion is 40 nnn. X70 nnii. in extent; thickness usually 1 nun., but some- 

 times up to 2 mm. around the periphery or in some parts of the 

 colonies. The animal encrusts reef corals, brown algae, the carapaces 

 of crabs, or the surface of solitary ascidians (e.g., Polycavpa crypto- 

 carpa^ as in the present material) . They are usually irregularly lobed 

 and, as a whole, the surface is smooth, though it may be depressed 

 slightly at the branchial aperture of each zooid or, contrastingly, 

 slightly elevated above strongly contracted zooids so that it assumes a 

 rough appearance as seen in one of the specimens from Palau. Gen- 

 erally, the superficial spicide-free layer is extremely thin or practically 



