Found under a rotting log, is this a nematode worm? And what type
No interactions present.
And many are parasitic, so seldom seen outside the host.
One zoologist said that if all other matter were removed, the outline of the earth's biosphere, including all other species, would be preserved in the nematode worms that remained behind. They are that ubiquitous.
There is one species that has adapted to live in the old-fashioned cork beer-mats...
Revision: the revision to Pot Worm is a good one, I think. Looking closely, it could well be segmented (and therefore not nematode). The point about size is good, too: most - not all - are tiny.
Certainly doesn't have the characteristic appearance of a nematode. The image isn't sufficiently close up for me to see if there are any chaetae(hairs) present and so I can't be sure its an annelid although the form of the gut (seen through the body wall) makes it look like one. There are certainly no features that confirm ID as an enchytraeid but the size and colour make this a reasonable bet
Lat/Lng: 51.2, -1.5
OS grid ref: SU3546