DISPERSION OF FRESH- WATER FISHES. \2J 



sible, and people finding them in such locaUties 

 often imagine that they have " rained down." 

 Once, near Indianapohs, after a heavy shower, I 

 found in a furrow in a corn-field a small Pike,^ 

 some half a mile from the creek in which he should 

 belong. The fish was swimming along in a tempo- 

 rary brook, apparently wholly unconscious that he 

 was not in his native stream. Migratory fishes, 

 which ascend small streams to spawn, are espe- 

 cially likely to be transferred in this way. By 

 some such means any of the water-sheds in Ohio, 

 Indiana, or Illinois may be passed. 



It is certain that the limits of Lake Erie and 

 Lake Michigan were once more extended than 

 now. It is reasonably probable that some of 

 the territory now drained by the Wabash and the 

 Illinois was once covered by the waters of Lake 

 Michigan. The Cisco ^ of Lake Tippecanoe, Lake 

 Geneva, and the lakes of the Oconomowoc chain, 

 is evidently a modified descendant of the so-called 

 Lake Herring.^ Its origin most likely dates from 

 the time when these small deep lakes of Indiana 

 and Wisconsin were connected with Lake Michigan. 

 The changes in habits which the Cisco has under- 

 gone are considerable. The changes in external 

 characters are but trifling. The presence of the 

 Cisco in these lakes and its periodical disappear- 

 ance — that is, retreat into deep water when not in 

 the breeding season — has given rise to much non- 

 sensical discussion as to whether any or all of 



1 Esox verniicidatus Le Sueur. 



2 Coregonus artedi sisco, Jordan. 



3 Coregonus artedi Le Sueur. 



