Note 378 — Chapter XI
Reading edition
"All Gasteropoda commence life under the same form, both of shell and animal, namely, a very simple helicoid shell, and an animal furnished with two ciliated wings or lobes, by which it can swim freely through the fluid in which it is contained. At this stage of existence the animal corresponds to the permanent state of the Pteropod, and the form is alike, whether it be afterwards a shelled or a shell-less species."—Prof. E. Forbes, Edin. Philos. Journal, vol. xxxvi. p. 326.
The well known Tiger Cowry (Cyprcea tigris) in its earliest stage has a minute helicoid (snail-like) shell.
[379] See Ly. p. 30.