88 Dr. 8. Lovén on a remarkable Sponge 
the amphidisci (birotulate spicula, Bow.) described and figured 
by Messrs. Bowerbank and Schultze. Spicules of this form 
are found, as far as hitherto known, among marine sponges, so 
perfect only in Hyalonema, and less pertect in Halichondria 
and in the freshwater genus Spongilla, where they are well 
known from the excellent and long-continued researches of 
Prof. Lieberkiihn*. In this genus they enter into the com- 
position of the envelope of the gemmules (ovaria, Bow.) in 
great number and in regular order. This kind of spicules 
accordingly is m connexion with the propagation. In Hyalo- 
nema Prof. Schultze searched in vain for such an arrangement; 
but this cannot be expected to be recognized in its primitive 
order in a dried specimen. If the specimens of our Sponge 
here described, so extremely small in comparison with the 
gigantic Hyalonema Sieboldi, were young, not yet prolific, or 
if the sexes were separated in this form of Sponges, the ab- 
sence of the amphidisci might be explained. 
The spindle-shaped needles of the stem of Hyalonema are 
of an immense length. The greater number of them reach 
from one end to the other; some of them are up to 0°67 metre 
long. The entire ones have their greatest thickness a little 
under the middle. The longest, though broken, needles have 
their thickest part nearer their free end. If this point is sup- 
posed to be at a distance of 0°5 metre from the end concealed 
in the interior of the sponge, then the longest needles, when 
entire, ought to have had the length of a metre, nearly eight 
times the longitudinal axis of the head. The longest needles 
of our sponge are not the fourth part of the length of the head. 
The stem of the Japanese sponge may have had the length of 
a single needle ; thirteen needles of the longest in our sponge 
would not, if laid end to end, have attained the length of the 
stem, which is, however, not more than thrice that of the 
head. ‘This great difference in the length of the needles can- 
not be entirely explained by the young state of the indivi- 
duals; their character of incomplete development, however, 
appears, as already remarked, by the comparison between 
their secondary forms, which in our Sponge are much less 
developed; and the same character is probably also indicated 
by the circumstance that in our Sponge the nodule very seldom 
receives transverse branches from the central canal, which 
appears to be a common case in Hyalonema. It may also 
be remarked that in Hyalonema the deposition of siliceous 
layers in the longest needles has gone so far that the nodule 
at the middle has been outwardly quite concealed, while its 
* Miller’s Archiv, 1856, pl. 15. f. 28, 29, 30; Bowerbank, British 
Spongiada, figs. 208-222, 317-319. 
