98 BULLETIN: 
MUSEUM OF 
COMPARATIVE 
ZOOLOGY. 
condition at a time, until the primitive types have been discovered. 
To this end future experiments must be directed — not toward the 
imitation of complex landscape conditions. The just interpretation 
J 
ON 
+ 
= 
; N 
It \ 
5 SN 
Yo ES 
E on 
| | Al 
7 | 
Ma MG KI 
of problems in river drainage can be rigorously attacked only after the 
primitive types have been worked out experimentally and some careful 
study given to the influence of each variable in the process. The 
