THE SPONGES. 93 



The deiiterocladi may exhibit a simple outward curvature. The deutero- 

 cladi are not always equal. In the same spicule some may ?je long and 

 curved, others much shorter and about straight. The dichotriaenes are 

 pretty closely set over the general surface, the cladomes overlapping. 



The dichotriaenes bordering the pore areas, both above and below, are 

 crowded, and many have smaller cladomes than the spicules elsewhere, the 

 deuterocladi being comparatively short and straight. Some spicules exhibit 

 a marked modification toward the protriaene condition, the protocladi 

 projecting strongly upward, while the deuterocladi are very short. Fig. 5, 

 Plate 12. 



^. Protriaene, Fig. 4, Plate 12. Among the modified dichotriaenes 

 which are found round the pore areas, perfect protriaenes occasionally 

 occur. In such spicules the cladi make an angle of 45° with the rhabdome 

 prolonged, and measure about 0.5 mm. by 70 />t. 



3. Anatriaene, Fig. 8, Plate 12. The spicules must be very rare, since 

 only two were found in a large number of preparations. These were both 



somal, and were alike in shape and similarly placed ; both broken. The 



spicules project from the surface of the body, along with the oxeas. 

 The rhabdome is about cylindrical, slender, 12 /u, thick in its upper part. 

 The cladome is deep; cladi about 200 ^ x 12 ^a, nearly straight, and 

 tapering evenly to a point. 



4. Oxea. a. Long, slender, nearly cylindrical oxeas, 6-7 mm. by 

 24-40 /a, project in closely set, diverging bundles over the upper surface 

 (Fig. 2, Plate 12). The arrangement in bundles is not well marked in 

 some places, the spicules in such places being more diffusely scattered. 



h. Much smaller, but similar oxeas, averaging 1400 /u, by 10 /x, project in 

 large numbers from the upper surface, between the basal parts of the larger 

 spicules. Similar oxeas project in large numbers over the lower surface. 



c. The oxeas of the parenchyma are chiefly arranged, along with the 

 triaene rhabdomes, to form radiating somal bundles, Fig. 2, Plate 12, but 

 are also scattered. They are mostly long forms, varying from a slender, 

 nearly cylindrical shape, 6-7 mm. x 20-30 /x, to a stouter, more fusiform 

 shape, 6-7 mm. x 90 /x. Shorter, slenderer forms occur, but not abun- 

 dantly, ranging down to 1.0 mm. x 10 />t. 



d. The oxeas of the roots are as a class very long. Slender, nearly 

 cylindrical forms, about 10 mm. x 30 /x, and stouter, more fusiform 

 spicules, 10 mm. x 90 fx, are both common. 



