88 Dr. S. Lov^n 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 liyalonema^ and less perfect in Halichondria 

 and in the freshwater genus Spongulaj where they are well 

 known from the excellent and long-continued researches of 

 Prof. Lieberkuhn*. 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 in 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 Sieholdi^ 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 reacli 

 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 



* Muller's Archiv, 1856, pi. 16. f. 28, 29, 30; Bowerbank, British 

 Spongiadffi, figs. 208-222, 317-319. 



