would exert control by virtue of topological position. An example of control of 

 this type is:**''' top consumers in a cold spring ecosystem model control the 

 bacteria, to which they are not at all directly connected, through a set of parallel 

 paths of indirect influence, whose first branch is a direct feedback linkage to 

 detritus which is only 1.4% of the value of total system input. Congeneric 

 homotaxis, as presented, is interesting but too direct factor oriented. "Congener" 

 means a closely similar functional form. The real basis for network stability, 1 

 would argue, is parallel paths, many of them, each carrying but a small portion of 

 the total influence between any pair of components. The paths may be very long, 

 and hence many species of many different functional types, i.e., noncongeners, 

 may be involved in them. Since the influence over any one path is small, 

 interruption of propagation over that path would have negligible effect on 

 system stability. This was the logic of MacArthur's original concept, which he 

 then went on to embody in the Shannon-Wiener function as a stability measure 

 (-Zp.logp,, Pi the probability of food transfer over the i'th path in the network): 

 "The amount of choice which the energy has in following the paths up through 

 the food web is a measure of the stability of the community."-" This amount of 

 choice, i.e., paths existing in parallel, increases combinatorially with the number 

 of species in the system. Thus, in context of the proliferation of parallel paths of 

 increasing length, which the present paper reveals as an inherent property of 

 system networks, MacArthur's original idea seems just as reasonable today as 

 when he originally proposed it. Community diversity confers path diversity 

 confers stability. If homotaxial congeners help maintain the integrity of parallel 

 paths, so much the better. The only thing MacArthur lacked was the transitive 

 closure formulation'^Jft for exhausting all the paths. 



REFERENCES 



1. Mason, H. L., and J. H. Langenheim. 1957. Language and the concept of 

 environment. Ecology. 38:325-430. 



2. Grinnell, J. 1917. The niche-relationships of the California thrasher. Auk. 

 34:427-433. 



3. Elton, C. 1927. Animal Ecology. Sidgwick and Jackson. London, England. 



4. Hutchinson, G. E. 1957. Concluding remarks. In Cold Spring Harbor Symp. 

 Quant. Biol. 22:415-427. 



5. Vandermeer, J. H. 1972. Niche theory. Ann. Rev. Ecol. Systemat. 3: 107-132. 



6. Levine, S. H. 1977. Exploitation interactions and the structure of ecosystems. 

 J. Theor. Biol. 69:345-355. 



7. Patten, B. CandG.T. Auble. 1980. Systems approach to the concept of niche. 

 Synthese. 43:155-181. 



8. Patten, B. C, and G. T. Auble. 1981. System theory of the ecological niche. 

 Amer. Nat. 117:893-922. 



9. Waddington, C. H. 1957. The Strategy of the Genes. Allen and Unwin. 

 London, England. 



10. Dawkins, R. 1978. The Selfish Gene. Oxford Univ. Press. New York, N.Y. 



1 1. Gibson, J. J. 1977. The Ecological Approach to Visual Perception. Houghton- 

 Mifflin. Boston, Mass. 



12. Turvey, M. T., and R. Shaw. 1979. The primacy of perceiving: an ecological 

 reformulation of perception for understanding memory. In Perspectives on 

 Memory Research. L. G. Nilsson, ed. Erlbaum. Hillsdale, N.J. 



13. Shaw, R., M. T. Turvey, and W. Mace. 1979. Ecological psychology: the 

 consequences of a commitment to realism. In Cognition and the Symbolic 

 Processes. Vol. 2. W. Weimer and D. Palermo, eds. Erlbaum. Hillsdale, N.J. 



14. Patten, B. C, and M. Witkamp. 1967. Systems analysis of 134 cesium kinetics 

 in terrestrial microcosm. Ecology. 48:813-824. 



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