Grass blazing in the darkness, effigies swinging from the gate, and the Humane Society threatening drastic action against torturers of pigs livened up the Yale campus yesterday in a prelude to today's game against Princeton.

Yale blamed a group of Princeton students for sneaking into the Yale Bowl Thursday night and burning a large black "P" into the field, while one observer reported an effigy of a Princeton student dangling from a New Haven gate.

At the same time, a spokesman for the New Haven Humane Society issued a warning to a number of Yale students who had planned to let several greased pigs loose on the Yale Bowl field. The schemers were informed that the first person to let loose a hog would be, in the unfriendly words of the Humane Society spokesman, "pinched."

Meanwhile, back at Princeton, seven Yalies took cans of blue paint and repainted the conservative white doors of several eating clubs with a revolutionary Connecticut blue.