OK — I 1 1 1 1 1 1 1 1 t I I I I . I 



6 7 8 9 10 11121314 15 1G17 1819 20 2I22 

 A;,'c in weeks 



Fig. i6. White mice grow faster in small groups than 

 in large ones; they grow slowest . when isolated (solid 

 line). (From Vetulani.) 



