

THE JOURNAL^ 



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THE PRESIDENT'S ADDRESS. 



SOME CONSIDERATIONS ON THE PHENOMENA 

 OF PARASITISM AMONGST PROTOZOA. 



By Prof. E. A. Minchtn, MA., F.Z.S. 



(Delivered February 22nd, 1910.) 



A LIVING organism, whether plant or a,nimal, which gains its 

 Hvelihood at the expense of another organism is termed a 

 parasite, and the organism at whose expense it lives is termed 

 its host. The conception of parasitism, therefore, implies an 

 antagonistic relationship between two correlated beings, parasite 

 and host, each of which has, so to speak, its own point of view, 

 the one attacking, the other defending. The phenomena of 

 parasitism are of most wide-spread occurrence, and very varied 

 in their nature. There is probably no species of non-parasitic 

 organism which is not liable to the attacks of some parasite, and 

 the same holds true even of a great number of parasites them- 

 selves, which are subject to be attacked in their turn by some 

 other parasite. 



The problems of parasitism are very complex, and are also 

 very important, both from the more abstract point of view, as 

 problems of natural history and bionomics, and also from the 

 practical point of view, in their bearing upon questions of 

 medical and veterinary science. In a brief space it is not 

 possible to discuss all aspects and problems of parasitism, nor 

 can such a discussion lay claim to any finality in the present 



JouRN. Q. M. C, Series II. No. m. 1 



