John D.April 12, 2012Just to clear a few things up - the 'urns' referred to in the novelization are the alien eggs.
The Alan Dean Foster novel was completed and readied for publication prior to the movie's release, and as such it was based on earlier drafts of the script. Some elements in the novel did not make it to the screen, while others date all the way back to Dan O'Bannon and Ron Shusett's original draft of the script, which you can read online at this link:
http://www.dailyscript.com/scripts/alien_early.html
The eggs are referred to as urns in two scenes in the script: once when the astronauts first enter the derelict and find an empty one (which presumably contained the creature that attacked the "space jockey") and again when the astronauts enter the pyramid (in this early draft, the pyramid full of eggs is still part of the story).
The script describes how the "urns" in the pyramid are exactly like the one found in the alien spaceship, but with one difference: they are all sealed. The text runs as follows:
(begin script excerpt)
Face bare, Broussard approaches the center of the room, which is
dominated by a large, broad pedestal. On the pedestal are ROWS OF
LEATHERY URNS OR JARS, EXACTLY LIKE THE ONE BROUSSARD STUMBLED ACROSS
IN THE ALIEN SHIP -- EXCEPT THESE ARE ALL SEALED.
He walks around the urns, studying them. They all have sealed lids. He
shines his light on one of them; then he lays his gloved hand on it.
He lifts his mask radio to his lips.
BROUSSARD
I don't know if you can hear me, but
the place is full of large bottles
or jars, just like the one we found
on the other ship -- except these
are all sealed. Also, they're soft to
the touch.
He peers more closely at the leathery object.
BROUSSARD (CONT'D)
Another funny thing -- I just put my
hand on it, and now there are these
raised areas appearing where my
fingertips were.
EXTERIOR - BASE OF PYRAMID - DAY
THE SUN DROPS BELOW THE HORIZON, throwing the landscape into gloom.
Standard and Melkonis switch on their lights.
STANDARD
Let's go.
He attaches his chest unit to the wire and starts up.
INTERIOR - TOMB - NIGHT
Broussard is moving his light along the rows of heiroglyphs on the
wall. They depict stylized drawings of strange monsters.
He pauses to quickly change the film clip in his datastick; then he
turns back to the "urn" he was examining -- BUT NOW THERE IS A HOLE IN
THE TOP OF IT.
He shines his light on the floor at the base of the "urn." There lies
the "lid" -- the stopper that had filled the hole. He picks it up and
studies it. It appears more organic than artificial; the inside
surface is spongy and irregular.
Then he turns the light to the now-open "urn."
He bends over the mouth of the "urn" shining the light in, AND WITH
SHOCKING VIOLENCE, A SMALL, OCTOPUS-LIKE THING LEAPS OUT AND ATTACHES
ITSELF TO HIS FACE, WRAPPING ITS TENTACLES AROUND HIS HEAD.
(/end script excerpt)
Notice they are described as leathery (which Kane says in the movie) and soft to the touch. Not very much like the stone- or metal-like objects depicted in the Prometheus trailer or images.
Scott, Lindelof or Spaihts may have revisited the idea of the alien eggs resembling 'urns' in order to re-use some of the discarded concepts from earlier versions of Alien, but it's safe to say that at no time during the production of the original film was any distinction made between 'urns' and 'eggs.' As far as the movie "Alien" was concerned, there was only the eggs, urn-like though they may be.
