DUBLIN MICROSCOPICAL CLUB. 
379 
take on dilferent modes of combination, and assume arrangements 
in themselves as yet supposed to be of generic import. Here, 
however, the cells themselves seemed to present an aspect un- 
usual ; if one could judge correctly, they seemed to offer a 
slightly tapering figure, but by no means comparable to that of 
the related GmnphospJiceria aponina, in which the cells are almost 
peg-top shaped, or, when partially divided, “ heart-shaped ; ” but 
the present plant agrees with that in the longitudinal direction 
of the line of self-division. Probably a characteristic connected 
with their slightly unequally-ended figure was that the last point 
of coniection between the Wo young cells not yet disjunct was 
not at the centre but notably nearer one end, thus increasing the 
resemblance (alluded to) to the opened but not sundered pair of 
cotyledons of a bean. In this plant the internal arrangement of 
the fittle granular and darkish masses of endochrome seemed 
peciliar. 
drains of Ruby in Australian sand. — Dr. Prazer showed some 
fine sand from Australia, taken from a river bed, many of the 
giains of which were of ruby, very pretty to look at under a low 
power, but far too small to be of any value. The sample had been 
^ven to him by the Rev. Mr. Whitmee. 
Modifications of structure presented in the cross sections of the 
spines of Goniocidaris caniculatus, G. tubariaf and G. geranoides. 
— Prof. Mackintosh exhibited cross-sections of the spines of 
Goniocidaris canicalatus, A. Agassiz, G. tubaria., Lamk., and 
G. geraniodes^ Lamk., and called attention to the interesting 
modification of the structure to be observed in them. In all 
three the central parts of the spine corresponded with the typical 
Cidarid arrangement. In the first named the peripheral crust 
was also sufficiently normal, there being no extensions of the 
intermediate part of the spine ; but in G. geranioides, as is well 
known, instead of the usual shell perforated by fine radiating 
tubules, there was an investment of reticulated tissue of the 
common echinoid type, supported by numerous extensions out- 
wards of the intermediate parts of the spine tissue. (Por figures 
of this form see Agassiz, ‘ Revision of the Echini,’ pi. xxx, and 
Mackintosh, ‘ Trans. Roy. Irish Acad.,’ vol. xvii, pi. ix.) In 
G. tuharia was seen the connecting form between the two ex- 
tremes, for there the crust is still more or less reticulated, but 
the projections into it are few and comparatively short. Prof. 
Mackintosh was indebted for the specimens, from which the 
sections had been made, to Prof. A. Agassiz, of the Harvard 
University. 
Minute quasi-par asitic Callithamnion on Lomeniaria articu- 
lata. — Dr. E. Perceval Wright exhibited some small morsels of 
the young fronds of Lomentaria articulata^ from the surface of 
which were to be seen in many stages of growth a very minute 
quasi-parasitic species of Callithamnion. It first made its ap- 
pearance as a single filament of four or five cells, protruding 
from some of the outer cells of Z. articulata / this soon branched, 
