A great deal of human play is serious--desperately serious on the football-field, and at the card-table, as when a lonely player is trying to kill time with solitaire. I have watched a great ungainly hippopotamus for hours trying to do the same solemn thing by cuffing a croquet-ball back and forth from one end of his cage to the other. His keepers told me that without the plaything the poor caged giant would fret and worry himself to death. It was his game of solitaire. In all their games of rivalry the animals are serious as humans, and, forgetting the fun, often fall to fighting--a sad case, indeed. But brutes are brutes. We cannot expect anything better of the animals. Only this morning the whole flock of chickens in the hen-yard started suddenly on the wild flap to see which would beat to the back fence and wound up on the “line” in a free fight, two of the cockerels tearing the feathers from each other in a desperate set-to. You have seen puppies fall out in the same human fashion, and kittens also, and older folk as well. I have seen a game of wood-tag among friendly gray squirrels come to a finish in a fight. As the crows pass over during the winter afternoon, you will notice their play--racing each other through the air, diving, swooping, cawing in their fun, when suddenly some one’s temper snaps, and there is a mix-up in the air. They can get angry, but they cannot laugh. I once saw what I thought was a twinkle of merriment, however, in an elephant’s eye. It was at the circus several years ago. The keeper had just set down for one of the elephants a bucket of water which a perspiring youth had brought in. The big beast sucked it quietly up,--the whole of it,--swung gently around as if to thank the perspiring boy, then soused him, the whole bucketful! Everybody roared, and one of the other elephants joined in with trumpetings, so huge and jolly was the joke. The elephant who played the trick looked solemn enough, except for a twitch at the lips and a glint in the eye. There is something of a smile about every elephant’s lips, to be sure, and fun is so contagious that one should hesitate to say that he saw an elephant laugh. But if that elephant didn’t laugh, it was not his fault. From the elephant to the infusorian, the microscopic animal of a single cell known as the paramœcium, is a far cry--to the extreme opposite end of the animal kingdom, worlds apart. Yet I have seen _Paramœcium caudatum_ at play in a drop of water under a compound microscope, as I have seen elephants at play in their big bath-tub at the zoölogical gardens.