Structure of Spongocladia , Aresch. 173 
of the department of Zoology, British Museum, kindly 
undertook to compare them with the spicules of other 
sponges, with the result that he found them to agree most 
closely with the spicules of a Halichondrine sponge. Not 
only this, but traces were soon discovered in abundance of 
the presence of the sponge itself, especially investing the 
whole of the apical portions of the branches of the thallus, 
giving them that characteristic grey and compact appearance 
already noted. Each branch bears therefore, without ex- 
ception, a cap of sponge bristling with spicules, and from 
the presence of these throughout the whole body of the 
Alga it may be inferred that with the growth of the branch 
the cap is carried upward, while groups of spicules and 
portions of sponge remain attached to the sides of the 
tubes. Of course, it is not to be forgotten that sponges 
frequently are to be found on Algae, and Mr. Kirkpatrick 
showed us, as being much to the point, Halichrondria panicea 
growing on Jania , as it may be seen on our own shores. 
In Spongocladia , however, there is an intimate relation of 
sponge with Alga of such a character as to suggest at least 
further inquiry. Accordingly the specimens of Spongodendron 
were brought into evidence. They came from another part 
of the world — from New Guinea. These, as has been said, 
are of two kinds, N. eras sum, Zanard., which we find indis- 
tinguishable from Spongocladia vaucheriae form is, by which 
name it will now be known, and S. dichotomum , Zanard., 
which now becomes Spongocladia dichotoma , Nob. 
In this New-Guinea specimen of S. vaucheriae for mis ( Spongo- 
dendron crassum , Zanard.) we have been unable to find in the 
limited portion at our disposal any trace either of an apical cap 
of sponge or indeed of sponge-tissue. But here again sponge- 
spicules are abundant, though not so much so as in the 
Mauritius specimens. The spicules are those of another 
sponge. In 5. dichotoma from the same locality spicules 
also are present to much the same extent, and they are 
those of yet another sponge. (It may be mentioned here 
that in S. dichotoma the walls are thinner and the septation 
