328 E. A. MINCHIN. 
bottom of a training ship moored permanently in the Porto 
Militare, growing amidst a thick crust of worm-tubes, 
Ascidians, sponges of various kinds, and other organisms. 
The colonies of Leucosolenia (Pl. 21, figs. 104—107) fre- 
quently attained a very large size, and were easily obtained 
from a boat by scraping the crust from the ship’s bottom; 
during which occupation the too enthusiastic naturalist might 
sometimes receive on his head objects or liquids of a peculiar, 
and even offensive, nature from the port-holes of the vessel. 
I made at that time a fairly complete study of the skeleton 
of this species of Leucosolenia, and found many errors in 
the published accounts of the spiculation. I will only refer 
at present to the peculiar slender monaxon spicules, shaped 
more or less like walking-sticks (PI. 21, figs. 120—122), which 
I have found always present, though previously undescribed, 
in this species, not only in Neapolitan specimens but also in 
those from Banyuls, and other parts. I regard these spicules 
as most diagnostic of this species. 
The triradiate systems (Pl. 21, figs. 109—114), both those 
with and those without an additional gastral ray, are, like 
those of other species of Leucosolenia, distinctly sagittal, 
having a straight unpaired “ posterior’ ray and two curved 
“lateral” rays. The “anterior” angle, between the paired 
rays, 1s greater than 120°; the lateral paired angles are less 
than 120°. The unpaired ray is sometimes shorter, more 
often longer, than the paired rays. 
In the accompanying text-figure I have represented the 
disposition of the triradiates in different parts‘of the sponges. 
I wish to state that, as regards form, the individual triradi- 
ates are represented diagrammatically in the text-figure 
without attempting to reproduce the exact form of the 
spicules; on the other hand, as regards position of the 
spicules, the figure claims to be exact. My method was to 
mount pieces of the sponge unstained in Canada balsam, and 
to draw with the camera lucida all the triradiates seen in the 
body-wall on the upper side of the tubes. Owing to the 
thinness of the body-wall the refringent spicules can be made 
