42 
Triassic Echinoderms of Bakony. 
At first I was unable tc detect any traces of this System on the epizygal 
face; but by gradually grinding it down and treating it with glycerine and alcohol, 
certain structures became visible through the microscope under a penetrating light 
(fig. 75). On grinding down to the level of the cirrus-lumina these structures became 
clearer, as I had anticipated, and revealed their true nature (text-fig. 5 B). In the 
centre of the lumen is a tiny white pentapetalon, with slightly marked lobes, in- 
terradially placed. Radially situated within the pentapetalon are five ovoid spaces, 
which are now darkened by the infilling calcite, but represent canals in the living 
animal — in fact the radial prolongations of the chambered organ. Hence it follows 
that the white specks seen on the hypozygal face represent, not the canals, but 
the thickened walls between them. There was no doubt a central canal, but too 
minute to be visible, so that its walls appear as a solid white mass. 
The ground section of the epizygal (fig. 76) shows the canals of the cirri 
passing to the columnar lumen, and swelling out as they pass across the joints 
between cirrals 1 and 2, and between cirral 1 and the columnar. Their entry into 
Text-figure 5. Axial nerves and vessels in an intersyzygium of Isocrinus candelabrum. 
A joint-face of the hypozygal, X 15 diam. B Central portion of the ground section of the epyzygal; 
the shaded decagonal area is the lumen, the white represents the walls of the vessels; X 65 diam. 
Both drawings are slightly diagrammatised from camera lucida Sketches. 
the lumen disturbs its interradially pentagonal outline, producing an irregulär decagon, 
or almost a radially oriented pentagon. From the radial sides of the central penta¬ 
petalon white streaks are just discernible, passing towards the radial angles of the 
lumen. These may represent in part Strands of connective tissue, specially needed 
to support the central axis at its nodal swelling, and in part the walls of the nerve- 
canals to the cirri. 
These remarkabty preserved structures afford interesting confirmation of the 
conclusions already derived from sections of the stem in the recent Isocrinus, as 
to the radial position of the prolongations of the chambered organ (proving the 
primitive possession of a dicyclic base), while the interradial direction of the angles 
of the lumen is seen to have been produced, probably by secondary formation of 
stereom, even at that early period. It has only been by repeated examination that 
I have succeeded in elucidating them, so that no time has been left in which to 
carry the research further. Traces of the same structures are however to be detected 
in the large specimen /, and I have no doubt but that their preservation will prove 
to be not so very uncommon. 
