276 



ERYLUS SOLLASII. 



uated; these turn one broad side towards the pore-canal and the edge towards 

 the outer surface of the sponge. Young and adult aspidasters also occur scat- 

 tered in the choanosome. In some specimens aspidasters are rather numerous 

 in the choanosome. In all parts of the choanosome acanthtylasters are met with. 

 These asters, particularly the small many-rayed ones, are more numerous in the 

 subcortical region than in the interior. In the spicule-preparations of race I, 

 form C, large smooth-rayed oxyasters up to 56 n in diameter, and in those of 

 race III small smooth-rayed oxysphaerasters (Plate 3, fig. 26b) have been ob- 

 served. I consider these asters, which were not found in situ in the sections, as 

 foreign spicules. About the foreign nature of the small oxysphaerasters in the 

 spicule-preparations of race III there can indeed be no doubt, as a Donatia-like 

 sponge-crust, containing such oxysphaerasters in large numbers, covers parts 

 of its surface. 



The rhahd megascleres (Plate 1, figs. 29-35, 42-48; Plate 3, figs. 19-22) 

 are for the most part blunt amphioxes (Plate 1, figs. 29-31, 33, 44-46; Plate 

 3, figs. 19, 20, 22). Besides these also sharp-pointed amphioxes (Plate 1, figs. 

 34, 35, 42, 43, 47, 48), amphistrongyles (Plate 1, fig. 32), and styles (Plate 3, 

 fig. 21) occur. Generally these rhabds are rather uniformly curved (Plate 1, 

 figs. 29-31, 33-35, 42, 43, 46-48; Plate 3, figs. 19-22), rarely straight (Plate 1, 

 figs. 32, 45), or abruptly bent near one end (Plate 1, fig. 44; Plate 3, fig. 18). 

 The styles and particularly the amphistrongyles are curved much less than the 

 amphioxes. The rhabds are 425-980 /x long and 8-24 pt thick. The longest are 

 found among the amphioxes, the thickest among the amphistrongyles and 

 styles. The small specimens, race I, forms A and B, have smaller rhabds than 

 the larger ones. Among the latter race I, form D, and race III have larger 

 rhabds than race I, form C, and race II. Besides these simple rhabds, spicules 

 similar in shape and size, possessing however a short branch-ray, are met with, 

 chiefly in race III. In these mesomonaene-like rhabd-derivates the branch-ray 

 (clade) is pointed or blunt, up to 50 /< long, and situated near one end, in styles 

 thus branched near the pointed end. The branch-ray is either turned upwards 

 proclade-, or downward anaclade-fashion. (See table, p. 277.) 



Most of the adult microrhahds (Plate 1, figs. 37-41a, 39b, 41b; Plate 2, 

 figs. 16-18; Plate 3, figs. 13-15, 26a) are quite stout, shghtly and uniformly 

 curved, centrotyle, isoactine amphioxes. Most of them are blunt, some sharp 

 pointed. Sharp-pointed microrhabds are particularly frequent in race III. 

 The blunt amphiox microrhabds are often somewhat constricted just below their 

 ends, so that the ends themselves appear as terminal knobs (Plate 2, fig. 18). 



