Until recently no Lemming remains had been found to the south of France, but Mr. Barrett-Hamilton announced to us a short time since that Dr. Gadow had discovered some skeletons with their skins still preserved in a cave in Northern Portugal. These were found to belong to the Scandinavian Lemming (_M. lemmus_), and the author incidentally expressed the opinion that there was some possibility of this species still inhabiting the mountains of Spain. The Lemming multiplies with great rapidity under favourable conditions. In speaking of his experiences in Siberia Dr. Brehm says (p. 79): "All the young of the first litter of the various Lemming females thrive, and six weeks later at the most these also multiply. Meanwhile the parents have brought forth a second and a third litter, and these in their turn bring forth young. Within three months the heights and low grounds of the tundra teem with lemmings, just as our fields do with mice under similar circumstances. Whichever way we turn we see the busy little creatures, dozens at a single glance, thousands in the course of an hour. But the countless and still increasing numbers prove their own destruction. Soon the lean tundra ceases to afford employment enough for their greedy teeth. Famine threatens, perhaps actually sets in. The anxious animals crowd together and begin their march, hundreds join with hundreds, thousands with other thousands, the troops become swarms, the swarms armies. They travel in a definite direction, at first following old tracks, but soon striking out new ones; in unending files--defying all computation--they hasten onwards; over the cliffs they plunge into the water. Thousands fall victims to want and hunger; the army behind streams on over their corpses; hundreds of thousands are drowned in the water or are shattered at the foot of the cliffs; the remainder speed on; other hundreds and thousands fall victims to the voracity of Arctic and red foxes, wolves and gluttons, rough-legged buzzards and ravens, owls and skuas which have followed them; the survivors pay no heed. Where these go, how they end, none can say; but certain it is, that the tundra behind them is as if dead, that a number of years pass ere the few who have remained behind and have managed to survive slowly multiply and visibly re-people their native fields." This eloquent passage reminds us of the manner in which migrations of all kinds of animals have taken place in former times, and are still taking place. It is principally want of food which compels them to search for new homes.