One of the simplest examples is furnished by the development of the Tubicolar Annelids; but from its very simplicity it appears well adapted to open the eyes of many who, perhaps, would rather not see, and it may therefore find a place here. Three years ago I found on the walls of one of my glasses some small worm-tubes (Fig. 65), the inhabitants of which bore three pairs of barbate branchial filaments, and had no operculum. According to this we should have been obliged to refer them to the genus _Protula._ A few days afterwards one of the branchial filaments had become thickened at the extremity into a clavate operculum (Fig. 66), when the animals reminded me, by the barbate opercular peduncle, of the genus _Filograna,_ only that the latter possesses two opercula. In three days more, during which a new pair of branchial filaments had sprouted forth, the opercular peduncle had lost its lateral filaments (Fig. 67), and the worms had become _Serpulæ._ Here the supposition at once presents itself that the primitive tubicolar worm was a _Protula,_—that some of its descendants, which had already become developed into perfect _Protulæ,_ subsequently improved themselves by the formation of an operculum which might protect their tubes from inimical intruders,—and that subsequent descendants of these latter finally lost the lateral filaments of the opercular peduncle, which they, like their ancestors, had developed. What say the schools to this case? Whence and for what purpose, if the _Serpulæ_ were produced or created as ready-formed species, these lateral filaments of the opercular peduncle? To allow them to sprout forth merely for the sake of an invariable plan of structure, even when they must be immediately retracted again as superfluous, would certainly be an evidence rather of childish trifling or dictatorial pedantry, than of infinite wisdom. But no, I am mistaken; from the beginning of all things the Creator knew, that one day the inquisitive children of men would grope about after analogies and homologies, and that Christian naturalists would busy themselves with thinking out his Creative ideas; at any rate, in order to facilitate the discernment by the former that the opercular peduncle of the _Serpulæ_ is homologous with a branchial filament, He allowed it to make a detour in its development, and pass through the form of a barbate branchial filament. _The historical record preserved in developmental history is gradually_ EFFACED _as the development strikes into a constantly straighter course from the egg to the perfect animal, and it is frequently_ SOPHISTICATED _by the struggle for existence which the free-living larvæ have to undergo._