I. Memmler 1943 Perognathus californicus June 9, M.V.Z. Corrugated card board carton 9 1/2 x 13 1/2 x 10 1/2 inches. I have covered the floor with about 2" of shavings. I made a nest out of excelsior and lined it with wrapping cotton. I have two watch glasses sunk into the shaving. One contains mixed field seeds, the other fresh grass, carrot, mallow and Melilotus. A water bottle is suspended into the box. The mice immediately took to the nest I prepared for them. They did not voluntarily come out to eat until about 3 p.m. Pat now has her pouches full and has gone back to the nest to work on it. They seem to prefer the dry seeds to the greens of various sorts placed in the box. June 10, I left Mike and Pat in their new box at M.V.Z. over night. I turned the radiator on for about an hour before leaving to warm the room up - and left plenty of food in the box. This is the first night since we found them that I have not taken them to bed with me to keep them warm. This morning the room was quite warm enough and the mice were warm when removed from their nest. Much dry seed and quite a bit of carrot,