J. L. BROOKS 111 



difficulties in their classification, considered below, it has been 

 difficult to grasp the problem in its entirety because the bulk of 

 the whitefish populations live north of the regions heavily popu- 

 lated by man. The numerous and diverse attempts following the 

 standard practices of ichthyology have resulted in cumbersome 

 systems employing many tri- and quadrinomials (see, for ex- 

 ample, Berg, 1948, and Hubbs and Lagler, 1947). The chief 

 source of difficulty has been the diversity of the morphological 

 and physiological characteristics of these Coregonus populations. 

 Not only does each major drainage system have its peculiar 

 forms, but also several forms may occur in any one lake. It was 

 not until the investigations by Gunnar Svardson into the biology 

 of the populations living in various Swedish waters that we have 

 had any insight into the nature of the systematic relationships 

 within this genus. The remainder of the discussion will be con- 

 cerned with the factors contributing to the difficulty of recog- 

 nizing species of Coregonus, as these factors have been uncov- 

 ered by Svardson in a series of papers (1949-1953). 



Unfortunately Svardson has not yet attempted to name the 

 species that his investigations have disclosed, nor has he at- 

 tempted to unravel the chaotic taxonomy of the genus. His 

 general feeling, however, is that the genus comprises two major 

 species groups (superspecies in the sense of Mayr). Svardson 

 calls these two superspecies the lavaretus group (after Corego- 

 nus lavaretns Linn.) and the albula group (after C. albula Linn.). 

 Not only are the species within each group nearly indistinguish- 

 able but even the two superspecies are also very similar. The 

 best character distinguishing the superspecies apparently is that 

 the lower jaw in species of the albula group is always longer than 

 the upper. The lavaretus group, on which all of Svardson's work 

 was done, has its greatest number of species in Europe and 

 western Russia, where the albula group is represented by a much 

 smaller number of species. In eastern Asia and in North America, 

 however, it appears that the albula group has formed many 

 species, whereas there are relatively few lavaret us-\ike species. 

 Walters ( 1955 ) pointed out that the glaciated portions of Eurasia 

 and North America have far more Coregonus species than do the 



