Here are the lyrics as I transcribed them:

COCKLES AND MUSSELS ALIVE ALIVE O!

Of all merry blades that ply merry trades,
Or win the affections of pretty young maids;
There is no one so trim or supple of limb
As light-hearted, ruddy-faced mussel man, Jim.
My musical sounds enliven my rounds,
I'm known the world over, from Stepney to Bow;
While singing aloud to a wondering crowd,
Fresh Cockles and Mussels alive, alive O!

ad lib: -         Alive, O! alive O!
Chorus. -        Alive, alive O! I call as I go,
Fresh Cockles and Mussels alive, alive O!

The fish that I sell are sound in the shell,
More luscious than oysters and feed you as well;
Fresh gather'd and good, they're excellent food,
To strengthen the nerves and replenish the blood;
They're just the right sort, a penny a quart,
On rocks where the mermaid sits singing, they grow,
No flounder or dab, periwinkle or crab,
Can equal my mussels alive, alive O!                Chorus.

There's young Polly Payne, tho' handsome, not vain,
She sells baked potatoes in Rosemary Lane;
And people do say, if fate has its way,
That we shall be married next Michaelmas Day,
And when she is mine, oh, won't it be fine
With two little stalls standing all of a row,
While folks passing by, will laugh as we cry-
Hot taters and mussels alive, alive O!                Chorus.

And if we contrive in business to thrive,
Which we shall most certainly do, if we strive,
My Polly and me as happy will be -
As two little birds on the boughs of a tree.
With something to spend, to give and to lend,
And little ones round us to chuckle and crow,
Those artful young imps who bawl out their shrimps
Will wish they sold mussels alive, alive O!        Chorus.

And nobody knows, the way the world goes,
What sort of good fortune there is in these clothes.
And some lucky year, I perhaps may appear,
As beadle churchwarden, or great overseer;
Or maybe sit down in an alderman's gown,
And wear a large belly as round as a bow;
And won't you all stare when I'm made a Lord Mayor,
From cockles and mussels alive, alive O!        Chorus.