Papers in the Biological Sciences


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Published in The American Naturalist, Vol. 27, No. 318 (Jun., 1893), pp. 509-520.


Symbiosis and mutualism, in the vegetable kingdom at least, are phenomena accompanying parasitism. Parasites have various effects upon their hosts, according to the nature of the parasite, its mode of life and method of attack. In some cases the host is quickly killed and the parasite becomes a sort of saprophyte upon the remains. In others the host lives longer or is only partially affected. In still others the host lives on side by side with the parasite indefinitely. A further development is attained in cases where the parasite and host not only live together, but are mutually beneficial, and, perhaps, even, in extreme cases, inter-dependent. To the first phenomenon -namely, the living together of parasite and host-DeBary, in 1869, in a work entitled Die Erscheinung der Symbiose, gave the name of Symbiosis. The latter phenomenon-i. e., mutual assistance or inter-dependence of parasite and host-was named mutualism in 1873 by Van Beneden in his "Animal Parasites and Messmates." Symbiosis in the strict sense and mutualism are often confounded, that is, the term symbiosis is often used to mean mutualism as such ; but, in strictness, while mutualism, in the case of plants, can only exist with symbiosis, in the larger proportion of cases of symbiosis there is no mutualism.

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