{229}[Illustration: FIG. 113.—_Lophocalyx philippensis._ The specimen bears several buds attached to it by long tufts of spicules. (After F. E. Schulze.)] [Illustration: FIG. 114.—_Leucosolenia botryoides._ A, a piece of the Sponge laden with buds, _a-f_; _i_, the spicules of the buds directed away from their free ends; _k_, the spicules of the parent directed towards the osculum, _j_. B, a bud which has been set free and has become fixed by the extremity which was free or distal in A. (After Vasseur.)] Such a reversal of the position of the bud is noteworthy in view of its rarity, and the case is worth reinvestigating, for in other animal groups a bud or a regenerated part retains so constantly the same orientation as the parent that Loeb,[257] after experimenting on the {230}regeneration of Coelenterata and other forms, concluded that a kind of "polarity" existed in the tissues of certain animals. In _Oscarella lobularis_[258] the buds are transparent floating bladders, derived from little prominences on the surface of the sponge. Scattered in the walls of the bladders are flagellated chambers, which open into the central cavity. The vesicular nature of the buds is doubtless an adaptation, lessening their specific gravity and so enabling them to float to a distance from the parent. GEMMULATION.—_Spongilla_ has already afforded us a typical example of this process. Gemmules very similar to those of _Spongilla_ are known in a few marine sponges, especially in _Suberites_ and in _Ficulina_. They form a layer attached to the surface of support of the sponge—a layer which may be single or double, or even three or four tiers deep. A micropyle is sometimes present in the spongin coat, sometimes absent; possibly its absence may be correlated with the piling of one layer of gemmules on another, as this, by covering up the micropyle, would of course render it useless. Presumably when a micropyle is present the living contents escape through it and leave the sponge by way of the canal system (Fig. 115). [Illustration: FIG. 115.—Gemmules of _Ficulina_. A, vertical section of gemmules _in situ_; B, vertical section of upper portion of one gemmule. _m_, Micropyle.] The only case besides _Spongilla_ in which the details of development from gemmules have been traced is that of _Tethya_.[259] Mere microscopic examination of a _Tethya_ in active reproduction would suggest that the process was simple budding, but Maas has shown that the offspring arise from groups of archaeocytes in the cortex, that is to say, they are typical gemmules. As they develop they migrate outwards along the radial spicule-bundles {231}and are finally freed, like the buds of the Hexactinellid _Lophocalyx_ (Fig. 113).