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In the latter no trace of hind-legs was visible, but the abdominal region was much emaciated and contracted, while the head region was broader. May 4. Noticed minute white buds of hind-legs in the thyroid-fed tadpoles. May 6. A number of the thyroid-fed were dying, and the skin and opercular membranes were swollen out away from the tissues beneath.
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 Protulae, 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.
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 Serpulae 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.
Making allowance for this it is evident that the tails had undergone reduction as part of the metamorphosis, but the body was also shorter. There is some reason therefore for concluding that actual reduction in size of body occurs as the result of metamorphosis induced by thyroid feeding. As in the other case the skin and opercular membranes were distended by liquid beneath them.
In the short period of a few weeks or months, the changing forms of the embryo and larvae will pass before us, a more or less complete and more or less true picture of the transformations through which the species, in the course of untold thousands of years, has struggled up to its present state. With a barbate opercular peduncle, Filograna-stage;
What say the schools to this case? Whence and for what purpose, if the Serpulae were produced or created as ready-formed species, these lateral filaments of the opercular peduncle?
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