ECOLOGICAL SUCCESSION. 25 



Hirkory Creek rises in a depression between two morainic ridges, 

 and that its upper course is sluggish and did not originate by 

 stream en-in. Its profile is shown in Fig. 3, page 19. 



The species of fi-.li n<>\v at the source of thi- -tivam could not 

 have filtered when this stream wa- young and have kept pace 

 with the migration .f conditions, because if thi- was a stream at 

 all during tin- close "f the glacial epoch, it wa- carrying the waters 

 from melting i( e "r a pond in the same manner a- it is now drain- 

 a mar-h. 



Tin- li-lie- or ~pi , ies of fi-h that are now found near tin- -ouree 

 of this -l ream wen- obliged to travel a di-tance of \~\\\- miles 

 through a murky niar-hy -tn-am to reach the headwaters. The 



success of mo-i of the - present in the -lu.^i-h upper course 



of thi- -ire, nil i- prolial>l\- due al-o \,> l,,c.tl artifici.il i'\po-ure of 



vel, since the set tlrmcnt of tlu- country. There ha> been dr. 

 in- to facilitate drainage. ^i\ of the thirteen >pecir> are known 

 to u-e bare hottoin lor hreediiv^ I rbes and Kichard-on -how 

 thai o| the leu . i| these uhich they . on-idered in their taldes 

 ( |)|. ci\ i \iii nine -ln>\\ a preference for the l>ot toin ( ,|" n , t -k and 

 -and. ^< Mile .1) lhe-e decided. 



Tin- xhou - that li-h may enter the headwater- of -(ream- 

 \\iihont ianicnlar reference to plu-io^raphic condition-. Hen- 

 po-iti\e rlieot.ixi- ma\ 1 e a fact.ir a-^ain l.\on, '04). 



Tin- observations of tin- .,f drought and llood tiirow 



further li^ht on the cause and rate of migration. 

 . ' on ///c . 1 - 



;';/ 



i. /'/.- fhere was an unusual drought in the autumn of 



[908. The ilata on the < li-tril >ut ion of li-hc- in ("ik-ncoe lirook 

 and ('oiinty Line ( 're.-k \\ ei . collected before tin'- dale. TaMe 



1\". -ho\\^ tin- arrangement the drought. 



< >imt\ Line Creek \\a- entirely dr> except the pool neare-t 

 its mouth in September. ; Thi- i- the locality marked 4 in 



. 2. The t"llo\\ini; spring \\a- OIK- of normal rainfall. The 

 fish proceeded Upi >nil\ three rods. Thi- partially 



re-tored the u-iial arrangement. If thi- repre-eiil- tin- rate, ti-li 

 proceed np-iream -lo\\l\. < ileiicoe Brook ha- not reco\'ered 

 it- ti-li. 



