SILICIOUS AND HORNY SPONGES WILSON. 279 



to be natural. It is a curious fact that directly in the center of the 

 inhalent membrane there opens a canal coming from the interior 

 of the sponge and quite unconnected with the surrounding vesti- 

 bular space, that is roofed over by the membrane. The areas are 

 different again in that the inhalent one is in all specimens con- 

 siderably larger than the exhalent. Both are circular or ellipsoidal 

 in outline. 



Spicules. — 1. Dichotriaenes, abundant, clads overlapping; rhab- 

 dome 1,800-3,500 by 70 p., protoclad 200 by 70 \i, deuteroclads 1,000- 

 1,150 [x long. 



2. Protriaenes; rhabdome reaches 4.5 mm. by 70 [x; clads 700 fx 

 in length, strong, curving. 



3. Oxeas. In the fringes the spicules are of the length of the 

 fringe and about 35 [>. thick. 



Similar slender oxeas, about 4 mm. long, often but not always 

 accompanying the rhabdomes of the triaenes; also projecting gen- 

 erally from the surface, along with smaller ones down to 700 fx long. 

 Stouter oxeas, usually somewhat curved, occur in interior, 4.5 mm. 

 by 70 [x. 



4. Anatriaenes. In the spicules of the body, clads 35-60 jx long, 

 rhabdome long and slender. 



Roots chiefly made up of very long, slender anatriaenes, with some 

 oxeas. Clads of anatriaenes reach length of 0.5 mm., with a basal 

 thickness about equal to that of rhabdome, 8-10 [x. Such anatriaenes 

 were only seen near the ends of long roots; probably no such roots 

 have been preserved in specimens of this species hitherto recorded. 



5. Streptasters. 



Plesiasters (pi. 45, fig. 1), very abundant throughout sponge, with 

 4 rays, ray length 80-140 [x. 



Metasters (pi. 45, fig. 2, a, b), also very abundant throughout 

 sponge; axis very short and curved, with 5-7 rays, ray length 

 20-36 [x. 



Spirasters (pi. 45, fig. 2, c), total length 24-36 jx, ray length 

 10-16 [x; rays about 9-12 in number. Very abundant in the fenes- 

 trated membranes of the aquiferous areas; much less abundant in the 

 general ectosome. 



All three classes of streptasters grade into one another. But the 

 intergrades are not numerous. The metasters, so designated by 

 Sollas, have so small a number of rays that they differ only slightly, 

 except in size, from the plesiasters. 



Sollas' specimens (1888) came from Australian waters. Thiele 

 (1898) records the type and eight subspecies from Japan. Lebwohl 

 (1914) also records the type from Japan. 



