266 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
into the basin by ordinary process of rainfall must have aided in keeping 
it filled to its capacity. 
I propose now to trace the steps which an ice-front lake of this sort 
might be expected to pass through as the ice retreated. 
Ficure 2. 
Diagrammatic contour map to show developmental changes in a temporary ice-front lake. 
Life History of a Temporary Ice-Front Lake. 
When the ice stands just back of a divide, it will form many little 
lakes at different levels. From the fact that valleys branch and re- 
branch headwards so that the number of little valleys is greatest near 
the divide, it follows that the closer the ice-wall is to the divide, the 
