Feeding, Breeding, and Development 17 



70 cm. long, 45 cm. wide, and 10 cm. deep in front, were 

 supported by a frame as is shown in Figure 3. The fact that 

 the covers of these cages cannot be left open is of practical 

 importance. A similar type of cage, which I have used to 

 some extent, consists of a wooden box 30 by 30 cm. by 15 

 cm. deep, without any bottom, and with a hinged cover made 



FIGURE 2. Double cage, with nest boxes and water dishes. 



in part of i cm. mesh wire netting. Such a cage may be 

 placed upon a piece of tin or board, or simply on a news- 

 paper spread out on a table. The advantage of the loose 

 bottom is that the box may be lifted off at any time, and the 

 bottom thoroughly cleansed. I have had this type of cage 

 constructed in blocks of four so that a single bottom and 

 cover sufficed for the block. If the mice are being kept for 

 show or for the observation of their movements, at least one 

 side of the cages should be of wire netting, and, as Kishi 

 suggests, such objects as a wheel, a tower, a tunnel, a bridge, 

 and a turntable, if placed in the cage, will give the animals 

 excellent opportunity to exhibit their capacity for varied 

 forms of activity. 



