This is the full text, from the New-York Historical Society:
The swirling mass of snakes and heads on this jug represent an important cast of characters in New York City's political history ... the Boss Tweed gang. The coiled snake on top is the handle for the jugs stopper. The Anna Pottery Company of Illinois made this as a thank you gift for Thomas Nast, a famous political cartoonist of the 1860s and 70s. Nast had used his cartoons to attack the massive misappropriation of public funds by Boss Tweed and his henchmen, who controlled the political machine known as Tammany Hall. Tweed is the bearded head without glasses, and most of the other heads are his associates. Also notice the behinds of all the Tammany Hall members trying to climb into the pot of money and power. A lot of people knew about Tweeds corruption, but it was Nast's cartoons in Harper's Weekly that finally aroused the public, the newspapers, and government officials to arrest Tweed and send him to prison. The pottery makers also added their hero Nast to the jug. He's the highest head on the jug, the one not attached to a snake's body. Today political cartoonists still see Thomas Nast's cartoons as the gold standard for their profession. And this sculpture stands as a testament to the power of artistic expression.