{Coregoniis artedi Le Sueur). 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 undergone are considerable. The changes 

 in external characters are but trifling. The presence of the cisco 

 in these lakes and its periodical disappearance — that is retreat 

 into deep water when not in the breeding season — has given rise 

 to much nonsensical discussion as to whether any or all of 

 these lakes are still joined to Lake Michigan by subterranean 

 channels. Several of the larger fishes, properly characteristic 

 of the Great Lake region (as, Lota lota maculosa; Percopsis 

 gtittatjis ; Esox niasquinongy) , are occasionally taken in the 

 Ohio river, where they are usually recognized as rare strag- 

 glers. The difference in physical conditions is probably the 

 sole cause of their scarcity in the Ohio basin. 



The similarity of the fishes in the different streams and 

 lakes of the Great Basin is doubtless to be attributed to the 

 general mingling of their waters which took place during and 

 after the glacial epoch. Since that period the climate in that 

 region has grown hotter and drier, until the overflow of the 

 various lakes into the Columbia basin through the Snake 

 river has long since ceased. These lakes have become isolated 

 from each other, and many of them have become salt or alka- 

 line and therefore uninhabitable. In some of these lakes 

 certain species may now have become extinct which still remain 

 in others. In some cases, perhaps, the differences in surround- 

 ing may have caused divergence into distinct species of what 

 was once one parent stock. The suckers in Lake Tahoe 

 {Catostomus tahoensis, in Lake Tahoe ; Catostomtis macrocheilus 

 and discobolus, in the Columbia; Catostonms fecundus, Catos- 

 tomus ardens ; Chasmistes Horns and Pantostens generosus^'xn 

 Utah Lake) and those in Utah Lake are certainly now different 

 from each other and from those in the Columbia. The trout 

 {Salnio mykiss, et vars. hcftshaivi and virginalis) in the same 

 waters can be regarded as more or less tangible varieties only, 

 while the whitefishes {^Coregomis williamsoni) show no differ- 

 ences at all. The differences in the present faunae of Lake 

 Tahoe and Utah Lake must be chiefly due to influences which 



