536 



BULLETIN OF THE BUREAU OP FISHERIES 



3 or 4 pounds are found in which the predorsal contour line is as smooth as in the 

 fish of the upper lakes. Such fish were particularly common off Merlin, Ontario, in 

 November, 1924. The principal systematic characters of the two forms that can be 

 expressed numerically are compared below: 



Pv/P: 



Michigan, (1.5) 1.7-1.9 (2.3). 

 Erie, (1.6) 1.7-1.9 (2). 

 Av/V: 



Michigan, (1.4) 1.6-8 (1.2). 

 Erie, (1.4) 1.6-1.7 (1.8). 

 L/D: 



Michigan, (3.3) 3.9-4.2 (4.8). 

 Erie, (3.1) 3.3-3.6 (3.8). 

 Pectoral rays: 



Michigan, (1.4) 15-17. 

 Erie, 13-15 

 Scale rows: 



Michigan, (46) 48-50 (52)-(36) 37-39 (40)- 



25-27 (28). 

 Erie, (45) 46-48 (50)-(34) 35-37 (39)-(24) 



25-27. 



Gill rakers on the first branchial arch: 



Michigan, (24) 26-28 (30)." 



Erie, (25) 26-29 (30)." 

 Lateral-line scales: 



Michigan, (74) 81-88 (93). 



Erie, (73) 77-86 (93). 

 L/H: 



Michigan, (4.4) 4.5-4.8 (5.3). 

 Erie, 4.7-5 (5.3). 

 H/E: 



Michigan, (4.4) 4.6-5. 

 Erie, (4.3) 4.8-5 (5.2). 



H/S: 



Michigan, (3.2) 3.4-3.8 (4.1). 

 Erie, (3.3) 3.4-3.8 (4). 

 H/M: 



Michigan, (3) 3.2-3.3 (3.7). 

 Erie, (3) 3.1-3.3 (3.7). 



The two forms are in close agreement in respect to all proportions except those 

 involving body depth, head in relation to total length and the eye, and it is probable 

 that this disparity would be reduced in the former and eliminated in the last two if 

 the specimens in the two groups were strictly comparable. In the matter of counts 

 there appear to be differences. The Erie form tends apparently to have fewer 

 pectoral rays, fewer scale rows, and possibly fewer lateral-line scales? but except 

 for the latter character too few specimens have been examined to permit any 

 conclusions. 



The color in fife is slightly paler than that described for Superior specimens. 

 The iridescence of the sides also is fainter and more often pinkish. Alcoholic speci- 

 mens show pigment distributed in the same manner as has been described for the form 

 from northern Lake Michigan, except that pigmentation is much less intense. 

 The smoky hue of the back and fins is much reduced. The pectorals are often nearly 

 immaculate. 



Pearl organs are developed in the breeding season by both males and females, 

 and their development is like that described for Huron specimens. 



VARIATIONS 



Racial variations. — No studies have been made to determine the occurrence of 

 local races. 



Size variations. — The only whitefish seen have been those that were marketable, 

 and there is not sufficient inequality in size to ascertain how the body changes with 

 growth. It is probable that such changes are like those outlined for the species in 

 other waters. 



w Figures for Lake Michigan are given for 52 specimens ranging in length from 300 to 483 millimeters, except that those for 

 gill rakers are given for 151 specimens, for lateral-line scales for 191, for pectoral rays and scale rows for 20. 



« Figures for Lake Erie are given for 18 specimens ranging in length from 291 to 402 millimeters, except that those for gill rakers 

 are given for 100 specimens and those for lateral-line scales for 324. 



