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effected .. abruptly by a few stages; ... but the transformations are in reality numerous and gradual, though concealed. A certain ephemerous insect (Chlöeon) during its development, moults, as shown by Sir J. Lubbock, above twenty times, and each time undergoes a certain amount of change; and in this case we see the act of metamorphosis performed in a primary and gradual manner. Many insects, and especially certain crustaceans, show us what wonderful changes of structure can be effected during .. development. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. Such changes, however, reach their climax in the so-called alternate generations of some of the lower animals. It is, for instance, an astonishing fact that a delicate branching coralline, studded with polypi and attached to a submarine rock, should produce, first by budding and then by transverse division, a host of huge floating jelly-fishes; and that these should produce eggs, from which are hatched swimming animalcules, which attach themselves to rocks and become developed into branching corallines; and so on in an endless cycle. The belief in the essential identity of the process of alternate generation and of ordinary metamorphosis has .. been greatly strengthened by Wagners discovery of the larva or maggot of a fly, namely the Cecidomyia, producing asexually ... other and similar larvæ. .. .. .. .. ..
It has already been stated that various parts and organs in the same individual are exactly like each other during an early embryonic period, but in the adult state become widely different and serve for widely different purposes. So again it has .. been stated that the embryos of the most distinct species within the same class are generally closely similar, but become when fully developed widely dissimilar. A better proof of this latter fact cannot be given than that by Von Baer,