The difference between the gemmule-spicules of this species and those of such a form as _T. phillottiana_ is merely one of degree and can hardly be regarded as a sufficient justification for placing the two species in different genera. If, as I have proposed, we confine the generic name _Tubella_ to those species in which the gemmule-spicules are really like "little trumpets," the arrangement is a much more natural one, for these species have much in common apart from the gemmule-spicules. _T. pennsylvanica_ does not appear to be very closely related to any other known species except _T. phillottiana_. TYPE in the U.S. National Museum, from which specimens that appear to be co-types have been sent to the Indian Museum. GEOGRAPHICAL DISTRIBUTION.--Very wide and apparently discontinuous:--N. America (widely distributed), Ireland (_Hanitsch_), Hebrides of Scotland (_Annandale_), Travancore, S. India (_Annandale_). The only Indian locality whence I have obtained specimens is Shasthancottah Lake near Quilon in Travancore. BIOLOGY.--In Shasthancottah Lake _T. pennsylvanica_ is found on the roots of water-plants that are matted together to form floating islands. It appears to avoid light and can only be obtained from roots that have been pulled out from under the islands. In Scotland I found it on the lower surface of stones near the edge of Loch Baa, Isle of Mull. In such circumstances the sponge is of a greyish colour, but specimens of the variety _minima_ taken by Potts on rocks and boulders in Bear Lake, Pennsylvania, were of a bright green. Sponges taken in Travancore in November were full of gemmules; in my Scottish specimens (taken in October) I can find no traces of these bodies, but embryos are numerous. Genus 6. TUBELLA, _Carter_. _Tubella_, Carter, Ann. Nat. Hist. (5) vii, p. 96 (1881). _Tubella_, Potts (_partim_), P. Ac. Philad. 1887, p. 248. _Tubella_, Weltner (_partim_), Arch. Naturg. lxi (i), p. 128 (1895). TYPE, _Spongilla paulula_, Bowerbank. This genus is distinguished from _Ephydatia_ and _Trochospongilla_ by the fact that the two ends of the gemmule-spicules are unlike not only in size but also in form. It sometimes happens that this unlikeness is not so marked in some spicules as in others, but in some if not in all the upper end of the shaft (that is to say the end furthest removed from the inner coat of the gemmule in the natural position) is reduced to a rounded knob, while the lower end expands into a flat transverse disk with a smooth or denticulated edge. The spicule thus resembles a little trumpet resting on its mouth. The shaft of the spicule is generally slender and of considerable length. The skeleton of the sponge is as a rule distinctly reticulate and often hard; the skeleton-spicules are either slender or stout and sometimes change considerably in proportions and outline as they approach the gemmules.