ECOLOGICAL SUCCESSION. 13 



to a lesser degree. \Ye believe that workers in this line have had 

 in mind the recognition of activities, but the subject is too new 

 to make such an id< lizable in practice. 



It is the purpose of this paper to present some details of the 

 di-iriliutii'ii of ti-h which -hall throw light on the limitations and 

 application- of tin- principles which Adams set forth. 



The pre-entation "I data and the discussion are based on the 

 following que-tion-: 



1. Are the h>h of the headv. < !' older -ttvam- the >ame as 

 the fi-h of younger streams? 



2. It SO, did they uei into tin- -tream \\hen it wa- yung and 

 -imply keep |iacr \\ith tin- advance "t ero-ion into the land.-' 



.}. \\'lial i- tin- relation o| the ,i<ti\itie- of animals to their 

 di-t ributioii in -t ream 



t 



4. What aspects "!' -i of purely local and what are 



o| -eiier.il -i^nitii ai 



II. LOCALITIES \\l> M \ i l Kl \l Si i mi .i'. 

 In l he ii itioii "I problem- in ait\ tield, one ot the thin 



rei|uirin- p-eal care is the selection of material. In the Mud\ ot 



ecology, if il i- l" be lied \\iih particular ^puip-, ihi- i- 



triii-, and in addition a still wore inifxirtiiti! n :u.\t he made, 



nameK . //.'.// c/' !/:< !>< dtiti ''v. 



I . i ' ' '.'/. 



I Of ihi- -tlld\ ti-h \\en- -elected bec.m-e lhe\ are probably 

 ihe onl\ .inimal- that are not introduced \>\ accidental mean-. 

 'l'he\ inii-t ha\e eiitrred the streams -tudied at their mouth-. 



2. The Points of Stn<Iy. 

 I or the purposes of this study, the ii>h of several -mall >t reams, 



\\ithin forty mile- of Chicago, have been collected. These 

 -tream- are all indicated on the map. 



(a) Present Condi! i> 



Beginning \\ith the mo-t northerly on the map, the -t reams are: 



Util! Creek-Dead River. It extend- in\\anl about three fourths 



of a mile from the boundary of old Lake Chicago ( >ee map), and 



divide- into t\\<> main brandies, each of which has a number of 



