I owe Syd for this enchanting discussion of the "WHY?" question I posed in my earlier post. It is magical nature says Syd. An old friend says this current photo of the banana slug is "very yin and yang of them." Whatever. They are fascinating conversation.
In answer to my poem which actually said:
Elegy for a Slug
Why didn't God
throw him a shell?
A shell is actually buried under the slug's mantle. But unlike the familiar spiraling shells of snails, this one is only a thin, fragile membrane of calcium carbonate that is barely noticeable. It hardly deserves to be called a shell.
But the shell leaves a clue that slugs evolved from shell-bearing snails. The slug's shell is a vestige of a distant past. It is a perfect example for Darwin's exquisite logic: "Rudimentary organs may be compared with the letters in a word, still retained in the spelling, but become useless in the pronunciation, but which serve as a clue in seeking for its derivation.
On the view of descent with modification, we may conclude that the existence of organs in a rudimentary, imperfect, and useless condition, or quite aborted, far from presenting a strange difficulty, as they assuredly do on the ordinary doctrine of creation, might even have been anticipated, and can be accounted for by the laws of inheritance."
Most shells are used to keep animals from drying out and not to protect the soft body within. But the slug has a lot of mucus that keeps its body moist. See how magical nature is?
3 hours ago