62 ART. 1. — I. IJIMA : HEXACTINELLTDA, III. 



into the interstices of the basidictyonal plate, without becoming 

 soldered to the latter. 



The basidiclyonalia (PI. V., fig. 13) form a dense, irregularly 

 meshed reticulum of beams, the surface of which is thickly beset 

 with sharply pointed conical spines. The beams may be 40 1^ 

 thick; the spines, as long as 15/^-. Notwithstanding the irregu- 

 larity in the arrangement of the beams, it is not difficult to 

 make out that these are fundamentally nothing else than synap- 

 ticularly fused rays of hexactins and sometimes of pentactins also. 

 The rays in these basidictyonal spicules do not exceed 135 /^ in 

 length. Sometimes small, thick-rayed and nearly or quite smooth- 

 surfaced "hexactins are met with, lying free in close proximity to 

 the spiny beams. They seem to represent early stages in the 

 formation of basidictyonalia, before the soldering together has 

 set in. This takes place wherever the sj)icules come in contact 

 with one another. The spiny processes on a beam may grow so 

 as to touch and fuse wâtli another beam lying close by, thus 

 transforming themselves into synapticulœ. (In fig. 13, PL V., is 

 seen a spiny siliceous ring standing in connection with basidictyonal 1 

 beams. This is an accidental formation, without doubt due to 

 the same siliceous secretion, as thai: which is added to the surface 

 of the beams, having taken place around some round object which 

 no longer remains in the preparation). 



As regards the dennalia, it would be well to mention first 

 those of quite young specimens (PI. V., fig. 9). In these, they 

 ai-e nearly all, if not exclusively, pentactins of approximately the 

 same ray-length as an average-sized parenchymal hexactin in the 

 same individual. The unpaired ray is of course directed proximad. 



