1 74 Murray and Boodle. — On the 
and branching of the filaments less frequent.) In addition to 
these forms Dr. Grunow very kindly sent us another species, 
not hitherto published, which he had collected in New Cale- 
donia, which we have described under his name of »S. neo- 
caledonica. Its habit is more diffuse, and in fact the thallus 
can hardly be described as branching at all. The filaments 
which compose it are of great diameter and contain abundance 
of starch. In this form we find still fewer spicules and no 
trace of sponge. The spicules here again belong to a sponge 
different from all the others. 
Are we to regard this occurrence of sponge and of sponge- 
spicules in all these instances as accidental? Taken by itself, 
the case of N. neocaledonica , for example, we confess might 
easily be so explained. Taken together with these other 
forms from other parts of the world in which spicules were 
more abundant than they usually are on Algae growing 
among sponges ; taken especially with the case of N. 
vancheriaeformis , we venture to think the subject presents 
another aspect. It is possible that we have here some bio- 
logical relation between sponge and Alga. Farther than this 
suggestion of inquiry we should not be justified in going on 
the material at our command. It would certainly be inter- 
esting to know whether such biological relation, if any, is 
concerned with nutritive adaptation. 
We append a systematic account of the genus, in which 
we have adopted so far as possible the descriptions of 
Areschoug and Zanardini. Areschoug’s generic characters 
have been so amended as to admit vS. neocaledonica. As to 
its systematic position it is scarcely advisable to speak very 
definitely, but it certainly appears to come nearer Cladophora 
than any other type known to us. 
SPONGOCLADIA. — Aresch. in Oversigt af Kongl. Vetensk. 
Akad. Forhandl. 1853. 
Alga viridis, adnata, filis cellularibus laxe implexis con- 
texta. Fila unica cellularum serie constructa, inferne parce 
