2 Proceedings of the Royal Society of Victoria. 



A transverse section shows a cylindrical canal occupying the 

 organic centre and a series of canals, which are somewhat 

 reniform in transverse section, arranged round this in several 

 concentric circles. The canals are connected with those on the 

 same radius by very fine tubules, connection of one canal with 

 another beside it occurring rarely in the sections I have examined. 

 The whole structure has therefore very much the appearance of 

 an Haversian system of a mammalian bone, but the central 

 canal is smaller and the fine tubules corresponding to the 

 canaliculi are far fewer and coarser than in bone. 



In longitudinal section the canals are seen as parallel tubes, 

 and the connecting tubules, which are far apart, run, as a rule, 

 somewhat obliquely from one canal to another. In one instance 

 a " tabula " crossing a large canal was clearly seen. 



A longitudinal section through the point where branching 

 takes place shows that the central canal itself divides into two, 

 a division running up the axial line of each branch. The fine 

 tubules occasionally pierce the outer wall of the cylinder and 

 their openings form the slitlike pores before mentioned. Some 

 of the specimens of which I have made sections are infiltrated 

 with iron pyrites, which has filled even the fine tubules, and the 

 structure is thus more clearly shown than in those specimens 

 where no infiltration has taken place. 



In the recent condition the members of the genus, as restricted 

 by MacGillivray, are fixed to foreign bodies by a fiexible organ 

 of attachment, which is built up of alternate calcareous and 

 chitinous portions resembling, as Lamouroux remarks, the stem 

 of fsts. The rooting apparatus is very variable in form and in 

 the amount which is in contact with the usually pointed stalk 

 {stiel of Kirchenpauer). Near its origin the calcareous portions 

 are disc-like, but towards its distal portion become more elongate, 

 and the rooting organ breaks up into cylindrical jointed twigs 

 which branch copiously and frequently anastomose. Branching 

 always takes place from the calcareous segments. The latter 

 vary very much in length. The ultimate ramifications consist of 

 a single hairlike tube which becomes firmly attached to a foreign 

 body such as a rock or fragment of a molluscan shell, and in 

 which the alternations of calcareous and chitinous segments is 

 clearly visible, and in which branching and anastomosis also 

 occur. 



