Barriers to Dispersion of River Fishes 315 



to any existing barriers between the river and the Great Lakes. 

 In northern Indiana the watershed is often swampy, and in 

 many places large ponds exist in the early spring. 



At times of heavy rains many species will move through con- 

 siderable distances by means of temporary ponds and brooks. 

 Fishes that have thus emigrated often reach places ordinarily 

 inaccessible, and people finding them in such localities often 

 imagine that they have "rained down." Once, near Indian- 

 apolis, 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 temporary - 

 brook, apparently wholly unconscious that he was not in his 

 native stream. Migratory fishes, which ascend small streams to 

 spawn, are especially likely to be transferred in this way. By 

 some such means any of the watersheds in Ohio, Indiana, or 

 Illinois may be passed. 



Fig. 193. — Creekfish or Chub-sucker, Erimyzon sucetta (Laci^p^de). Nipisink 

 Lake, Illinois. Family Catostomidw. 



It is certain that the Hmits of Lake Erie and Lake Michigan 

 were once more extended than now. It is reasonably prob- 

 able that some of the territory now drained by the Wabash 

 and the Illinois was once covered by the waters of Lake Michi- 

 gan. The ciscof of Lake Tippecanoe, Lake Geneva, and the 

 lakes of the Oconomowoc chain is evidently a modified de- 

 scendant of the so-called lake herring, t Its origin most likely 



*Esox vermiculatus Le Sueur. t Argyrosomus sisco Jordan. 



J Argyrosomus artedi Le Sueur. 



