SILICIOUS AND HORNY SPONGES WILSON. 359 



on the wall of which are the apertures of numerous small efferent 

 canals. There is the usual extensive root tuft at the lower end by 

 which the sponge is fastened in the mud. 



The Albatross specimens very generally are somewhat clavate, 

 enlarged and rounded above, smaller below. A typical specimen 

 is 45 mm. long, exclusive of root tuft; 12 mm. thick above, 6 mm. 

 thick about middle of body, with a cloaca 6 mm. deep. Some small, 

 doubtless young, ones, 12 mm. long by 2.5 mm. thick, were taken. 

 The dense sponge parenchyma contains abundant embryos. The 

 color is light brown, verging on lead gray, but there is reason for 

 believing that the natural color in this species is purple red or yellow 

 (Carter 1887). In my specimens, as in Dendy's (19166), conspicu- 

 ous bundles of spicules pass obliquely downward and outward from 

 a point just below the floor of the cloaca. At this point the begin- 

 nings of the bundles are aggregated, forming a little mass (" skeletal 

 nucleus ") that is sometimes conspicuous. These bundles reach the 

 lower end and adjoining region, from which they enter into the root 

 tuft or project freely from the surface. 



From the ectosome in general well-marked radial bundles of 

 megascleres are prolonged into the interior. Between these are 

 numerous scattered megascleres. The ectosomal megascleres them- 

 selves are arranged in close-set divergent (conical) brushes, each 

 brush including some large oxeas and many very slender pro- 

 triaenes, most of which project only a short distance, but some far 

 beyond the surface. The ectosomal brushes as seen in surface 

 preparations are sometimes distinct and separate from one another, 

 sometimes continuous with one another. 



The spicule measurements, as determined for a few of these speci- 

 mens, increase, but not greatly, the range of recorded sizes. 



1. Oxea, tapering gradually from middle to the sharp points, 

 1,500-2,000 by 14-16 [jl, in the ectosomal and internal bundles. In 

 Lendenf eld's Tetraxonia (1903) 60 \l is given as the thickness of the 

 oxea — obviously a misprint. (See Sollas 1888, p. 44.) 



Smaller oxeas of same type, 450-900 by 6-8 jx, scattered every- 

 where. 



2. Ectosomal protriaenes, very slender. Rhabdome 2 pi thick, prob- 

 ably 2-3 mm. long (difficult to isolate whole) ; clads, making an 

 acute angle with one another, even thinner than rhabdome, hair-like 

 and about 50 \i long. 



Stouter protriaenes project here and there from the lower surface. 

 Rhabdome 6-7 [/. thick, several mm. long. Clads 3 \l thick at the base, 

 tapering to the point ; varying in length but reaching 120 \l ; making 

 an acute angle with one another. 



3. Anatriaenes. Rhabdome 4-6 \i. thick, several mm. long; clads 

 44-48 [l long; making up the root tufts; abundant also in down- 



