Ripley : [watching Ash examine the creature] That's amazing. What is it? Ash : Uh, yes, it is. Umm. I don't know yet. Did you want something? Ripley : Yes, I, uh... have a little talk. How's, uh, how's Kane? Ash : He's holding, no changes. Ripley : And, uh, our guest? Ash : Umm. Ripley : Hmm? Ash : Well, as I said, I'm still... collating, actually, but uh, I have confirmed that he's got an outer layer of protein polysaccharides. Has a funny habit of shedding his cells and replacing them with polarized silicon, which gives him a prolonged resistance to adverse environmental conditions. Is that enough? Ripley : That's plenty. What does it mean? [Ripley bends down to look through the micro-scanner] Ash : Please don't do that. Thank you. Ripley : I'm sorry. Ash : Well, it's an interesting combination of elements making him a... tough little son-of-a-bitch. Ripley : And you let him in. Ash : I was obeying a direct order. Remember? Ripley : Ash. When Dallas and Kane are off the ship, I'm Senior Officer. Ash : Oh, yes, I forgot. Ripley : You also forgot the Science Division's basic quarantine law. Ash : No, that I didn't forget. Ripley : Oh, I see, you just broke it. Hmm? Ash : Look, what would you have done with Kane, hmm? You know his only chance of survival was to get him in here. Ripley : Unfortunately, by, uh, breaking quarantine, you risk everybody's life. Ash : Maybe I should have left him outside. Maybe I've jeopardized the rest of us, but it was a risk I was willing to take. Ripley : That's a pretty big risk for a Science Officer. It's, uh, not exactly out of the manual, is it? Ash : I do take my responsibilities as seriously as you, you know. You do your job and let me do mine, yes?

http://www.moviequotedb.com/movies/alien/quote_26916.html