A Remarkably Relevant Excerpt from Naomi Mitchison's Memoirs Of A Spacewoman.

When I finally came back to full time and being, we were in orbit round a world which seemed to consist on its surface of evenly convex hills thickly wooded, or at any rate covered in some way.  We could see no oceans, only occasionally a darkness which might be water between these round hills....

At first we did some straight old-fashioned exploring; I could find no species with which to get into communication, though there were some small forms scuttling mouselike or crablike through interstices of the thick growth which covered the hills, as well as some still smaller winged forms, often bright-coloured.  The predominant growth was actually of three kinds.  There was a tall, cylindrical, flexible growth which moved in a rhythmic way.  After watching these for a some time we realised that they had a very simple snapping head, two jaws -- but were they jaws or toughened, thick leaves?  -- which opened and closed and occasionally caught one of the winged forms, whatever they were.  There were somewhat thicker growth with feathery tops which waved and shivered; I felt that these were definitely animal, to use a rather archaic classification, and was prepared to watch carefully before making any observations which would result in destroying or injuring one of them.  And then there were curious and beautiful blunt-topped hexagonal forms, knobbed and striped and radiated in splendid colours.  What were they?  They were hard, rocky, perhaps, we thought, coralline.  For a time we had been unable not to think of them as artefacts, as columns of some extraordinary temple, and yet that seemed improbable, especially as they seemed to grow out of the underlying hard rock which was only, as far as we could make out, covered to a depth of a few centimetres with dust and debris....

A little more exploration took us down the slopes to the edge of the dark, curving lakes round the bases of the great, rounded hills.  There was no beach, only a thick clustering of the snappers which arched themselves into the top layer of the water -- it was water, though with a number of minerals in it in heavy solution, and quite undrinkable.  This top layer was packed with a life of a fairly low order; we took a number of specimens.  There were mats of vegetation, mostly large, single cells strung together, but some a little more complex, any amount of material for our taxonomists who had a lovely time comparing all this with lifeforms from other worlds in the same galaxy and elsewhere....

There had been some argument about getting down to the lake.  We had to push or edge our way with some difficulty between the snappers, the feathered plumes and the hard columns.  The snappers were perfectly harmless as far as we were concerned; there was nothing that could hurt even an ungloved hand....  One group wanted above all to find out what kind of world this was, what was the nature, reason for, and result of, these identical rounded hills, each of which -- about this time we had made our way on to several others -- had the same covering.  We found our inflating boats perfectly adequate and pushed our way through the snappers.  These were not hard enough to be more than a mild nuisance, even if they happened to catch one's arm or the blade of a paddle -- the lakes were too narrow to make any kind of engine necessary -- but we found they ingested pieces of malted bread with no trouble, and often used to feed them, especially if we wanted to quiet them while we made our own observations on the top layer of fauna and flora....

We were in two minds about investigation of the snappers and feathery growths.  They might have consciousness; one had seen forms as odd in other worlds; however, we did investigate those near the edge of our clearing; they seemed to have roots going down deep into the rocks.  But there was no evidence of consciousness.

...We did some experiments in situ, and found that the plumose type was a breather, though we could not see what it ingested.  Gradually we all began to wonder if there was some connection between the three forms, especially when we found that where the mineralogists had taken a column, the snapper next to it began to droop and become inactive, and the plumose forms did not expand fully....

From the top of our own hill we could see all round, one hill after another, all more or less alike, each divided from the next by a broader or narrower strip of dark, deep water.  I was up there looking out from between two columns....  The snappers waved above my head.  I began to concentrate and watch.  I felt suddenly that I was on the point of realising what was what in this world if only I could see the connections more....  It seemed to me that something curious was happening.  One of the further hills was very slowly rising, and at the same time two others seemed to sink.  Perhaps, I thought, this had happened before but we had never stayed long enough to notice.  One ceased to move; the others still seemed to be dropping into the sea, though it was difficult to be sure with these completely round and featureless objects all with the same covering.  Yes, one of them at least was going down.

And suddenly I realised that this landscape of columns and snappers was exactly what one sees under a low power microsope looking at a sea urchin.  These hills were simply enormous echinoderms....