336 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



The spherasters (pi. 47, fig. 10, a) are of the usual type with large 

 centrum and conical raj's; total diameter of the spicule about 60 y.. 

 They are abundant in the ectosome, especially just below the level of 

 the subdermal cavities. A few smaller ones occur in the outermost 

 stratum of the choanosome. 



The chiasters, tylasters of some writers, acanthtylasters of Len- 

 denfeld (pi. 47, fig. 10, b), are about 12 [x in diameter with small 

 centrum and about seven rays which are enlarged and spinose at 

 the end; rays appear simply tylote when seen at magnifications of 

 400-600. The spicules are crowded at the surface forming a dermal 

 crust; also abundant in the ectosome in general; also abundant in 

 the walls of canals in the choanosome. 



Chiasters with terminally spinose rays have long been known to 

 occur in several species. Lindgren (1898, p. 358) refers to this fact. 

 In D. (Stelletta) nux Selenka, the larger ectosomal chiasters are of 

 this kind (Thiele, 1900, p. 61 ) . In D. lyncuHum Authors such spicules 

 sometimes occur (Topsent, 1900, p. 295). In D. magna Kirkpatrick 

 (1903, p. 240) they are characteristic: also in the several varieties of 

 D. japonica described by Hentschel (1909, p. 372). Topsent in his 

 recent essay on Donatio, (1918) shows rays of this character in all 

 the species figured. Doubtless in some of the older descriptions the 

 spinelets have simply been overlooked. 



The choanosomal oxy asters (pi. 47, fig. 10, o) are common through- 

 out the choanosome, although less abundant than the chiaster. 

 Total diameter of spicule 30-40 \l; rays about 6-7 in number, spicule 

 often hex-radiate; centrum very small, rays long and tapering, 

 straight or curved. The rays sometimes bear a few, one to three, la- 

 teral spines, and are not infrequently bifid. Spicules transitional 

 to the chiaster now and then occur; intermediate in size; the rays 

 comparatively stout and bearing at the apex several short spinelets. 



The data given above make it plain that the Albatross sponge be- 

 longs to the type known as D. seychellensis. 



The difficulty in distinguishing species in Donatio, has been point- 

 ed out more than once. Sollas (1888) recognized D. lyncurium 

 (Linnaeus), D. ingalli (Bowerbank), D. nmza (Selenka), D. sey- 

 chellensis (Wright), D. multifda Carter, and recorded several other 

 insufficiently described and uncertain species. 



The species which Sollas recognized are distinguishable types, 

 whatever their genetic relationship may be and regardless of th< 

 fact that various kinds of intermediate forms exist. Their differ- 

 ential characteristics may be stated as follows: 



In D. seychellensis there are spherasters, chiasters (doubtless 

 characteristically acanthtylasters), and larger choanosomal oxyasters. 

 Cortex with extensive intracortical cavities, and only fibrous in its 

 deeper stratum. 



