most of those pics didn't look like roundworm to me, but of course this is only my opinion.
ascaris i've seen. the skin is very thick, like an earthworm and internal organs aren't visible. do you have a link to anywhere that shows large size roundworms (like those that you don't need a microscope to see) that you can see internal organs? i'd be curious to see.i've not seen all types, so i don't know.