96 



from the others. This group is not a single specis outlier, but the 

 largest group and the separation suggests a basic difference in 

 distribution between species-group N members and members of the other 

 groups. The membership of each species-group is presented in Table 10. 



By examining the constancy and fidelity of species-groups at the 

 various site-groups it is possible to achieve insight into the 

 distribution of the species-groups and perhaps into the controlling 

 ecological mechanisms. This process is called nodal analysis. 



The patterns of constancy and fidelity of the species-groups at the 

 site-groups is summarized in Figs. 38 and 39. The width of the rows and 

 columns is proportional to the size of the groups. Site-group 1 is 

 occupied in medium to very high constancy by all species-groups with the 

 exception of species-groups H-K. These latter four groups also 

 demonstrate a fidelity of less than unity at site-group 1 indicating an 

 avoidance of the member stations. It is the only site-group where 

 species-groups E, F and M are highly constant and G and M are highly 

 faithful. With the exceptions of species-groups F and G, site-groups 2 

 and 3 are occupied by similar species-groups but differ in relative 

 constancy and fidelity especially in terms of species-groups A, B and C. 

 Site-group 4 is best characterized by the presence of species-groups I 

 and N. Species-group I is highly constant and faithful only at 

 site-groups 4 and 5. These two mid-Bay site-groups differ from one 

 another in that site-group 4 has six species-groups present at low to 

 medium constancy which do not occur at site-group 5 stations. 



Site-group 6 is impoverished. Only species-group J is present at 

 moderate constancy. Site-group 7 has similarities to site-groups 2 and 



