From the North Sea. 87 
canal-system, which Prof. Schultze here describes; and it is 
difficult to explain the extraordinary circumstance that these 
openings, which are so important to the life of the sponge, 
should have their place where it is adherent to the rock, and 
where the current issuing from them would meet with such 
resistance. 
By an incision in the head (‘the sponge”) Prof. Schultze 
laid open its inner structure. The stem (‘the coil”’) is con- 
tinued, as in our sponge, deeply into it; and the spicules of the 
head, inserted among the larger ones of the axis in the form 
of flattened strings or blades, are regularly disposed all round 
“the axis.” The figure (M.Schultze, ‘ Die Hyalonemen,’ pl. 2. 
f. 1) shows, though rather indistinctly, this structure, which 
accords well with that of our sponge. The parenchyma of the 
specimens examined by Prof. Schultze, was very much dimi- 
nished by drying. 
It is evident that the stem (‘the coil’’) of all the specimens 
of Hyalonema described has been torn off at its free end. 
Professor Schultze expressly states that its long needles are 
all broken; they are of the same type of form as those of 
our sponge—spindle-shaped, more or less round, thickest at 
the middle, tapering towards both ends, and somewhat spirally 
bent. The thickest part of many of the smaller and those of 
middle size has an inflation or nodule, in the interior of which 
the central canal gives off two short transverse canals, at right 
angles and in opposite directions. All this is as in our 
Sponge. From this simple primary type of spicule a number 
of secondary, more complicated forms are derived, almost 
without exception the same as in our Sponge, although in the 
latter not so fully developed. Such are the spicules with 
graduated ends (/. c. pl. 3. f. 5, 6, 7, our figs. 24, 25) or studded 
with short spines, into which the canal does not enter (/. c. pl. 3. 
f. 1-4, 9-15, our fig. 26), or with branches in two or four 
crossing directions (/. c. pl. 4. fig. 1, our figs. 14,19) ; but 
those of Hyalonema are strongly and perfectly developed, 
forming six-rayed needles, or five-rayed ones where one part 
of the primitive needle is lost (/.¢. pl. 4. £3, 5,6). There can 
be a branch also in only one side (/.c. pl. 3. f. 15, to compare 
with our figs. 15, 18). Whether the arcuated spicules without 
nodules, found in the dermal layer of our sponge (figs. 6, 35), 
are to be recognized in the spicules figured by Prof. Schultze 
(pl. 3. f. 2,3) may be left undecided. 
Besides these affinities, there are also differences. In addi- 
tion to the spindle-shaped needles, Zyalonema has also another 
type of siliceous spicules, which are not to be found in the 
specimens of our sponge I have examined. It is the type of 
