HYALONEMA (OONEMA) BIANCHORATUM PINULINA. 309 



Canal-system. The pores of the dermal sieves on the outer side of the body- 

 lead into wide canals extending into the interior. Other still wider canals extend 

 up to the gastral sie\'es on the inner face of the cup. Between these wide canals, 

 the former of which are, no doubt, afferents and the latter efferents, a tissue is 

 found containing narrow canals, and rather densely packed small flagellate 

 chambers (Plate 84, fig. 2). The sections of these flagellate chambers (Plate 

 84, fig. 2a) are mostly circular or broad-oval and 50-120 n in maximum diameter. 



The colour of both specimens in spirit is greenish brown. 



The skeleton. The poreless parts of the surface and the strands forming 

 the pore-sieve nets are, both on the dermal and the gastral face, covered by 

 a dense pinule-fur (Plate 83, figs. 45b, 61, 62). Under the poreless tracts of 

 both faces paratangential, more or less centrotyle amphioxes and the lateral 

 rays of pentactine megascleres form a superficial (hypodermal, hypogastral) 

 skeleton. The strands of the dermal pore-sieve nets are supported by the 

 lateral rays of hypodermal pentactines and a few centrotyle amphioxes (Plate 

 83, fig. 62). The centra of the pentactines are here usually about 700 ai apart. 

 In the gastral pore-sieve nets no pentactines have been found. Here centrotyle 

 amphioxes, congregated in dense bundles, alone occupy and support the strands 

 of the reticulation (Plate 83, fig. 61). 



Numerous centrotjde amphioxes, rather scarce hexactine megascleres, 

 and masses of microhexac tines occur in the choanosome. Some of the micro- 

 hexactines have straight, others curved rays. I think it not improbable that 

 the former, which are much the scarcer, line the walls of the wide main canals, 

 and are to be considei'ed as canalaria; while the latter are imbedded in the 

 choanosomal tissue, and are to be considered as parenchymaUa. 



Four kinds of amphidiscs can be distinguished : — large and small macram- 

 phidiscs, and large and small micramphidiscs. The large macramphidiscs are 

 rather scarce in both specimens and confined to the choanosome, where they 

 appear to be irregularly scattered. The small macramphidiscs are very numer- 

 ous on and in the gastral membrane of specimen a, where most of those seen 

 in situ in the sections were found to lie between the distal rays of the pinules 

 wholly outside the sponge, with their shafts vertical to the surface (Plate 83, 

 fig. 4oc), while only a few are scattered irregularly in the gastral membrane. 

 On the dermal face of this specimen small macramphidiscs have also been 

 observed, but they are here not nearly so numerous. In specimen h these amphi- 

 discs are similarly situated but much less abundant. The large micramphidiscs 

 are very rare in both specimens, the small very numerous in 6, but somewhat 



