SILICIOUS AND HORNY SPONGES WILSON. 335 



Genus DONATIA Nardo (1833). 



Dnnatia Nardo. 1S33. p. 522— Thiele, 1903, p. 965. 



Tethya Authors. — Lenpenfeld, 1S96, p. 16 (older synonymy in detail). 



Sponge usually of more or less spheroidal form, but sometimes a 

 flattened crust. Ectosome distinctly differentiated from the choano- 

 sorae, constituting a cortex which is more or less fibrous and which 

 lacks special microrhabds. Megascleres are rhabds, usually fusiform 

 styles or subtylostyles. Microscleres are spherasters together with 

 smaller eu asters of one or two sorts. 



DONATIA INGALLI (Bowerbank), var. SEYCHELLENSIS (E. P. Wright). 



Plate 47, figs. 9, 10. 



Tethea inyaUi Bowerbank, 1872, p. 119. 

 Alemo scychellensis Wright, 1881, p. 13. 



The species as here conceived (see below) covers D. ingalli 

 (Bowerbank), D. maza (Selenka), D. seychellensis (Wright), and 

 D. japonica Sollas. 



A specimen of the variety was taken at station D5181. Sponge is 

 spheroidal, 25 mm. in diameter, considerably incrusted with shelly 

 debris opposite the oscular process. 



Over most of the surface the conules are conspicuous conical pro- 

 jections very generally produced into slender gemmiferous processes. 

 The pores form irregular areas between the conules. There is a 

 single osculum at the end of an oscular process, the latter 8 mm. 

 long and 2 mm. wide. 



The ectosome is colorless and in general about 2 mm. thick, thinner 

 in the depressed areas and thicker in the conular regions. It is fi- 

 brous in its deeper stratum (pi. 47, fig. 9, /. s). Its outer stratum; 

 is much interrupted with subdermal spaces and pore canals. The 

 choanosome is greenish in color. 



There are the usual strong radial bundles (pi. 47, fig. 9) extending 

 from the center, expanding and subdividing in the cortex into narrow 

 brushes which support the dermal membrane. The styles making up 

 the radial bundles taper toward both ends and measure 1,600-2,000 

 by 28-32 |i, 



The styles of the surface brushes range from small ones, 500 by 

 8-10 [x, up to the larger spicules just mentioned. 



In the outer half of the choanosome, between the radial bundles, 

 there are abundant styles more or less radially arranged, those in the 

 immediate neighborhood of the radial bundles inclined obliquely to 

 the latter. The spicules commonly range from 500 by 12 [x to 1,000 

 by 18 fx, with some larger ones 1,800 by 32 jx. 



The central ends of the radial skeletal bundles are bound to- 

 gether by small styles, about 400 by 12 fx, forming a dense aggrega- 

 tion or " nucleus." 



