Answer:
Long and slinky like a trout, never sings till it's guts come out.
By Moon or by Sun, I shall be found. Yet I am undone, if there's no light around
What must be in the oven yet can not be baked? Grows in the heat yet shuns the light of day? What sinks in water but rises with air? Looks like skin but is fine as hair?
It has no top or bottom, but it can hold flesh, bones, and blood all at the same time.
I can run but not walk. Wherever I go, thought follows close behind.
You can always find me in the past. I am created in the present, but the future can not change me. What am I?