Ripley: Micro changes in air density, my ass.
Parker: It's a robot. Ash is a god damn robot.
Ripley: Ash, can you hear me? Ash!
Ash: Yes, I can hear you.
Ripley: What was your special order?
Ash: You read it. I thought it was clear.
Ripley: What was it?
Ash: Bring back lifeform: Priority One. All other priorities rescinded.
Parker: The damn Company! What about our lives, you son of a bitch?
Ash: I repeat: all other priorities are rescinded.
Ripley: How do we kill it, Ash? There's got to be a way of killing it. How...how do we do it?
Ash: You can't.
Parker: That's bullshit!
Ash: You still don't understand what you're dealing with, do you? The perfect organism. Its structural perfection is matched only by its hostility.
Lambert: You admire it.
Ash: I admire its purity: survival unclouded by conscience, remorse or delusions of morality.
Parker: Look, I've heard enough of this and I'm asking you to pull the plug.
Ash: Last word.
Ripley: What?
Ash: I can't lie to you about your chances, but you have my sympathies.
Ripley: Ash, that transmission... Mother's deciphered part of it. It doesn't look like an S.O.S.
Ash: What is it, then?
Ripley: Well, I... It looks like a warning. I'm gonna go out after them.
Ash: What's the point? I mean by the, the time it takes to get there, you'll... They'll know if it's a warning or not, yes?
Answer: According to the commentary on the DVD, Ridley didn't add this scene to the original cinematic release because he thought it revealed the true horror of the Alien too soon in the film. The scene is quite early in the film and he thought revealing the fully matured Alien at that time would reduce the viewer's fear.
I had watched Alien several times before I noticed the Alien hanging there.At this point the Audience have no idea what the Alien looks like, they're looking at pieces of science fiction equipment put in by the production crew that they can't relate to, so for all they know the Alien could just be a piece of kit hanging there.