40°35' N. (Hudson River, N. Y.) and the other 

 extending south of latitude 40^56 ' N. (North 



Sea Harbor, Long Island, N.Y.). The two groups 

 overlapped in the vicinity of latitudes 40'-'35' to 

 40°56' N,, but based on differences in sample 

 means, maintained their separate identity. The 

 means of the two groups differed in 1956 by 

 0.44 vertebra and in 1957 by 0.37 vertebra. 



A similar pattern was shown by the means 

 of the 1958 and 1959 year classes, but the 

 means of the two groups differed in 1958 by 

 only 0.29 vertebra and in 1959 by 0.26 verte- 



bra. Heterogeneity of sample means within 

 localities was not indicated for either year 

 class probably because of the paucity of sam- 

 ples from estuaries in the vicinity of lati- 

 tudes 40°35' to 40°56' N. 



Variation within groups 



Analysis of variance to determine the varia- 

 tion of means within groups (table 3) showed 

 heterogeneity within the southern group in 

 1956 and within the northern group in 1957. 

 This heterogeneity does not necessarily indi- 

 cate the existence of additional groups, but 



Table 3. — Analysis of variance of mean vertebral numbers of juvenile Atlantic menhaden 

 to test for homogeneity within groups, 1956-59 



Year class 

 and group 



Source of 

 variation 



Degrees 

 of freedom 



Sum of 

 squares 



Mean square 



1956 

 Northern. . . . 



Southern 



1957 

 Northern. . . . 



Southern. . . . 



1958 

 Northern. . . . 



Southern. . . . 



1959 

 Northern. . . , 



Southern, . . . 



Localities. . 



Samples 



Individuals . 



Localities. . 



Samples 



Individuals . 



Localities. . 



Samples 



Individuals . 



Localities. . 



Samples 



Individuals . 



Samples 



Individuals . 



Localities. . 



Samples 



Individuals. 



Localities. . 



Samples 



Individuals. 



Localities. . 



Samples 



Individuals. 



10 



3 



1,333 



26 



19 



4,319 



10 



13 



2,U8 



24 



42 



6,190 



1 

 196 



4 



4 



884 



1 



1 



248 



5 



10 

 1,525 



11.39 



1.24 



406.60 



13.81 



7.83 



1,077.98 



16.82 



5.73 



620.48 



17.71 



14.20 



1,496.80 



0.66 

 50.61 



1.31 



0.72 



209.68 



0.03 



0.57 



71.29 



0.64 



0.80 



378.52 



1.14 

 0.41 

 0.30 



0.53 

 0.41 

 0.25 



1.68 

 0.44 

 0.29 



0.74 

 0.34 

 0.24 



0.66 

 0.26 



0.33 

 0.18 

 0.24 



0.03 

 0.57 

 0.29 



0.13 

 0.08 

 0.25 



2.78 

 1.32 



1.29 

 1 1.64 



1 3.82 

 1.52 



2.18 

 1.42 



2.54 



1.83 

 0.75 



0.05 

 1.96 



1.62 

 0.32 



P < 0.05. 



