458 



BULLETIN OP THE BUREAU OF FISHERIES 



however, that such differences are due to the difference in size of specimens examined 

 from'the two lakes. Those from Lake Michigan were chiefly over 20 centimeters 

 in length, while those from Lake Huron were all smaller. 



VARIATIONS 



Racial variations. — There appears to be a racial differentiation according to 

 habitat in the same locality, which is manifested by rather conspicuous structural 

 changes. Below are compared, for seven characters, five groups of specimens, two 

 taken from depths of 30 fathoms or less, two from depths of 60 fathoms or more, 

 and one group from Cheboygan, Mich., taken in a gang set from 35 to 50 fathoms. 

 One group in each of the first two habitats was collected at Alpena, Mich. The others 

 originated in other parts of the lake, but confirm the comparison. The specimens of 

 the various groups are of comparable size. 



Gill rakers on the first branchial arch 



No. 



30 fathoms 



Harbor 

 Beach 



Alpena 



Total 



60 fathoms 



Alpena 



Georgian 

 Bay 



Total 



30-50 

 fathoms, 

 Cheboy- 



37. 

 38.. 

 39. 

 40. 

 41.. 

 42., 

 43. 

 44.. 

 45. 



1 

 0 

 7 

 6 

 17 

 18 

 16 

 8 

 1 

 3 

 1 



Lateral-line scales 



No. 



30 fathoms 



60 fathoms 



35-50 

 fathoms, 



Harbor 

 Beach 



Alpena 



Total 



Alpena 



Georgian 

 Bay 



Total 



Cheboy- 

 gan 

















1 





1 





1 









0 





2 



2 



4 



3 



2 



5 



1 





0 



6 



5 



2 



6 



8 



2 





2 



5 



7 



2 



4 



6 



5 





13 



6 



19 



15 



4 



19 



6 





10 



14 



24 



8 



12 



20 



8 





17 



14 



31 



29 



12 



41 



6 





14 



7 



21 



24 



11 



35 



6 





12 



25 



37 



32 



16 



48 



7 





14 



21 



35 



27 



9 



36 



6 





15 



21 



36 



28 



20 



48 



7 





11 



18 



29 



29 



14 



43 



12 





6 



12 



18 



18 



8 



26 



3 





4 



7 



11 



8 



10 



18 



2 





4 



3 



7 



10 



6 



16 



3 





1 



5 



6 



11 



1 



12 



3 







1 



1 



4 



0 



4 







2 



2 



4 



3 



3 



6 













0 



2 



2 













0 



1 



1 













1 





1 





















