66 UNITED STATES NATIONAL MUSEUM BULLETIN 251 



stratum, especially densely around the common cloacal aperture (fig. 

 20^) . In the colonies from GVF sta. 25, also Palau Islands (USNM 

 11379), the purplish pigment is concentrated between the zooids and 

 give the colonies a rather finely areolated appearance. 



Spicules are usually distributed densely and evenly from the bottom 

 to the surface of the colony, but they may be rather sparse as a whole or 

 above the individual zooids in some colonies ; in the latter cases the sur- 

 face of the colony appears spotted with many small, slightly darker 

 ovals. In some colonies from the Philippine Islands, the test is 

 slightly swollen above the zooids and some minute prominences formed 

 by aggregated spicules are scattered between these swellings ; this evi- 

 dently shows an intermediate state between the typical and next gran- 

 ulated forms. The superficial spiculeless layer is practically indis- 

 cernible on some colonies, but rather conspicuous in others. The 

 colonies densely impregnated with spicules but without the distinct 

 superficial spiculeless layer are somewhat rigid in consistency and 

 rather rough to the touch, while those with the thick superficial spicule- 

 less layer generally show a very smooth appearance on the surface. 

 The size of spicules varies considerably, from 17 to 55/i. in diameter 

 in the colonies examined. They are 20-24/^ in Australian specimens, 

 28-33jLi in a Japanese colony, 17-28/^, 33-39/i,, 41-55/x, and exceptionally 

 up to 64/i, in specimens examined from the Palau Islands. In some 

 colonies spicules are slightly larger along the periphery than in the cen- 

 tral part of the colony, and in the colonies densely packed with spicules 

 they are slightly smaller than in the colonies with sparcely distributed 

 spicules. Eays of spicules are short and blunt or truncate at the tip 

 in the typical form, although they may be rather slender and with the 

 tip acute or truncate in some colonies; the number of rays on the equa- 

 torial plane varies from 6-9 to 11-15. Thoracic lacunae distinct and 

 spacious; hypoabdominal lacuna absent. Even in thicker colonies 

 zooids are situated in the surface layer of less than 1.5 mm. in thickness, 

 while the lower part is a compact mass of spicules and contains fertil- 

 ized eggs or embryos. The common cloacal apertures are elliptical 

 or roundish in outline, and larger ones may be 3 mm. in long diameter. 

 Usually zooids are missing in the considerably wide area surrounding 

 the cloacal aperture. 



There are four small, whitish compact masses of spicules in the 

 material from the Palau Islands from GVF stas. 30 and 220. They 

 are roundish or oval in outline, less than 5 mm. in length and up to 

 2 mm. in thickness. They contain no zooids within the test. Spicules 

 are distributed evenly from the bottom to the surface, but slightly 

 denser in the lowest part; they are of the typical moHeleyl-iovm and 

 with G-IO, most frequently 7-8, rays on the equatorial plane. For 

 this reason, these masses are identified provisionally as Didemnum 

 moseleyi. 



