A. From specimen taken in July in a tank on the Calcutta maidan. B. From type specimen of _Ephydatia indica_ taken in the Indian Museum tank in winter. Both figures × 240.] _Spicules._ Skeleton-spicules feebly curved, slender, as a rule irregular in outline, sometimes almost smooth; the ends as a rule sharply pointed, often constricted off and expanded so as to resemble spear-heads, occasionally blunt. No true flesh-spicules. Gemmule-spicules often free in the parenchyma, cylindrical, slender, very variable in length in different sponges, straight or nearly so, as a rule with an irregular circle of strong straight or recurved spines at either end resembling a rudimentary rotule, and with shorter straight spines scattered on the shaft, sometimes without the rudimentary rotule, either truncate at the ends or terminating in a sharp spine. _Gemmules_ small, free, each surrounded by a thick granular layer in which the spicules stand upright or nearly so, and covered externally by a delicate but very distinct chitinous membrane; no horizontal spicules; foramen situated at the base of a crater-like depression in the granular coat, which is sometimes raised round it so as to form a conspicuous rampart; a short, straight foraminal tubule. The shape of the spicules is extremely variable, and sponges in which they are very different occur in the same localities and even in the same ponds. It is possible that the differences are directly due to slight changes in the environment, for in one pond in Calcutta a form with _Spongilla_-like gemmule-spicules appears to replace the typical form, which is common in winter, during the hot weather and "rains." I have not, however, found this to be the case in other ponds. Perhaps _S. hemephydatia_ will ultimately prove to be a variety of this very variable species, but its smooth and regular skeleton-spicules and short-spined gemmule-spicules afford a ready method of distinguishing it from _S. crateriformis_. The two sponges are easily distinguished from all others in the subgenus _Euspongilla_ by the upright and regular arrangement of their gemmule-spicules, for although in _S. proliferens_ and _S. travancorica_ some of the gemmule-spicules are nearly vertical, their arrangement is always irregular, a large proportion of the spicules make an acute angle with the inner coat of the gemmule and a few as a rule lie parallel to it. The systematic position of _S. crateriformis_ is almost exactly intermediate between _Euspongilla_ and _Ephydatia_, to which genus it has hitherto been assigned. I think, however, that taking into consideration its close relationship to _S. hemephydatia_, it is best to assign it to _Spongilla_, as its rudimentary rotules never form distinct disks. I have examined some of Potts's original specimens from different American localities and can detect no constant difference between them and Indian specimens. TYPES in the United States National Museum; co-types in Calcutta.