OF WASHINGTON. 7 



F. Based upon the number of hosts : 



1. Monoxenous parasites. 



2. Heteroxenous parasites. 



In conclusion I will state that the foregoing remarks are, in 

 large part, based upon the writings of Leuckart, Looss, R. 

 Blanchard, Railliet, Neumann, and others ; the division of 

 parasites proposed is a combination, with slight modifications, 

 of the divisions followed by these authors. 



Mr. Fernow objected to the definition of the word parasitism 

 as given by Dr. Stiles, and believed that the definition should 

 make it necessary for the parasite to not only obtain its food, but 

 also its domicile from its host, which would exclude such animals 

 as the mosquito ; and, further, that the parasite should, in some 

 stage of its existence, be entirely dependent on or unable to exist 

 apart from its host. He would further limit it also by making it 

 necessary that the food should be taken from the living host in a 

 form ready for immediate assimilation, arid which would exclude 

 vegetable-feeding animals, whose food would necessarily have to 

 go through a more or less elaborate process of digestion. Thus, 

 in general, plants only can be parasitic on plants, and animals on 

 animals. 



Mr. Hubbard believed, with Mr. Fernow, that the definition in 

 question was open to criticism, and was of the opinion that the 

 principle of absolute dependence at some stage, mentioned by 

 Mr. Fernow, should be present. He gave various examples of 

 mess-mates, etc., illustrating this idea. 



Mr. Doran mentioned other cases of parasitism in animals other 

 than insects and not referred to by Mr. Stiles. Some of these 

 cases, as pointed out by Mr. Stiles, were association for copulation 

 only. In reference to the limitation mentioned by Mr. Fernow, 

 viz., that the parasitic relation could only be sustained by mem 

 bers of the same kingdom, as animals on animals, etc., Mr. Stiles 

 took issue on the ground that no sharp lines should be drawn 

 separating plants from animals, and gave certain cases where such 

 association of plants and animals is certainly parasitic, such as 

 ringworm. 



Mr. Fernow replied that for all practical purposes, and in the 

 general estimation, there is a distinct separation of plants from 

 animals, and maintained the validity of his former restriction. 



