In the larva of _C. blanca_, after a period of free-swimming existence, the same three elements are thus recognisable as in that of _Sycon_ at the time of hatching; in the newly hatched larva of _C. blanca_, however, one set of elements, the dermal cells, are not distinguishable. The difference, then, between the two newly hatched larvae is due to the earlier cell differentiation of the _Sycon_ larva.[254] Now consider the larva of _Leucosolenia_. It is hatched as a {228}completely flagellated larva; its archaeocytes are internal (as in _Sycon_); future dermal cells, recognisable as such, are absent. They arise, as in _C. blanca_, by transformation of flagellated cells; but (1) this process is confined to the posterior pole, and (2) the internal cavity is small and filled up with archaeocytes. Consequently the cells which have lost their flagella and become converted into dermal cells cannot sink in as in _C. blanca_: they accumulate at the hinder pole, and thus arises a larva half flagellated, half not; in fact, an amphiblastula. Or, briefly, in _Leucosolenia_ the larva at hatching is a parenchymula, and when ready to fix is an amphiblastula; and, again, the difference between the newly hatched larva and that of _Sycon_ is due to the earlier occurrence of cell differentiation in the latter. What completer transitional series could be desired? Turning to the Micromastictora, the developmental history already sketched is fairly typical (p. 172). The differences between Mega- and Micro-mastictoran larvae are referable mainly to the fact that the dermal cells in the latter become at once differentiated among themselves to form the main types of dermal cell of the adult.[255] The metamorphosis is comparable to that of _C. blanca_. Among Tetractinellida and Hexactinellida sexually produced larvae have not been certainly identified. Asexual reproduction takes place according to one of three types, which may be alluded to as (1) "budding," (2) "gemmulation," (3) formation of "asexual larvae." By BUDDING (Fig. 113) is meant the formation of reproductive bodies, each of which contains differentiated elements of the various classes found in the parent. A simple example of this is described by Miklucho Maclay in Ascons, where the bud is merely the end of one of the Ascon tubes which becomes pinched off and so set free. In _Leucosolenia botryoides_[256] Vasseur describes a similar process; in this, however, a strikingly distinctive feature is present (Fig. 114), namely, the buds have an inverse orientation with respect to that of the parent, so that the budding sponge presents a contrast to a sponge in which multiplication of oscula has occurred. In fact, the free distal end of the bud becomes the base of the young sponge, and the osculum is formed at the opposite extremity, where the bud is constricted from the parent.