Note 47 — Chapter V · EVOLUTION.

Curiously enough, while the Nudibranch, which is without a shell, possesses one during its embryonic life, there is another mollusc, Neritina fluviatilis, which possessing a shell in its subsequent life is without one during the early periods, and according to Claparède begins an independent existence, capable of feeding itself before it acquires one. See his admirable memoir on the Neritina, in Müller’s Archiv, 1857.