408 Illinois State Laboratory of Natural History. 



Table II. is an exhibit of the results of all the examinations, 

 the booty of the table giving the number of individuals of the 

 various host species examined, and the number of such hosts 

 infested by each of the nine parasites named in the head- 

 ings. The footings of the columns and the subjoined per- 

 centages give the number and per cent, of species and 

 individuals infested. On the right, one column gives the 

 number of kinds of parasites found in each host species, and 

 another the total number of individuals in the species 

 examined which were infested to any degree. A comparison 

 of the data in these two columns, note being taken of the 

 number of individuals examined in the several species, as 

 given in the first column, shows a marked variation among 

 the different host species in the number of kinds of parasites 

 harbored and in the number of individuals of each species 

 infested. It is seen that Aspidogaster is by far the most 

 widely distributed and abundant parasite ; that Cotylaspis, 

 Atax, and Conchophthirus must be classed as very frequent; 

 that the free distomid and Bucephalus are less common ; and 

 that the remaining three parasites occur but occasionally. 

 It is remarkable that at least two sufficiently examined 



