In lines 35-69, Prufrock arrives at a party—one he finds very much like countless others he has attended over the years. This fills him with a feeling of ennui, a word that means a "been there, done that" world weariness. He wonders if he has measured out his life in coffee spoons; in other words, if he has had essentially the same experience and conversation over coffee again and again at parties just like this with the same people.
Prufrock, in this section, imagines people assessing his appearance, such as his bald spot (which indicates he is getting older) and his thinness. But he also seems to have a burning desire to say something. He asks:
And should I then presume?
And how should I begin?
In lines 70–74, Prufrock imagines himself saying:
I have gone at dusk through narrow streets
And watched the smoke that rises from the pipes
Of lonely men in shirt-sleeves, leaning out of windows ...
I should have been a pair of ragged claws
Scuttling across the floors of silent seas.
These later lines suggest that Prufrock wishes to communicate that he has had experiences beyond these endless parties, an existence beyond the one he shares with this group of people. He has an interiority that is separate and apart from them. Not only does he have thoughts they know nothing of, but when he wanders the streets alone, he seems to have a sense of identification with the "lonely" men leaning out of their windows, smoking their pipes. He too is apart, an observer of life.
He then wants to communicate, as he ponders the difficulty of saying what is on his mind, that he wishes he were a crab or lobster, a "pair of ragged claws," alone on the bottom of the ocean. This image conveys his sense of deep alienation, and, as sea creatures presumably simply exist without much thought, reflects Prufrock's desire just to be, released from constant self-conscious introspection.
One imagined response that people at the party might have would be surprise that timid Prufrock is not saying what he always does, but saying something new. They might find it odd that he is expressing feeling alienated and surprised he is communicating that he has a life of his own beyond this particular community. It is also very possible that after their initial surprise, if they are as world weary and stuck in a rut as he is, they would go on as they always do and forget all about what he said, indifferent to him.