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ILLINOIS BIOLOGICAL MONOGRAPHS 



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Proteocephalids Occurring in Two or More Species op Fish 



Twelve Proteocephalid species have been found to occur in more 

 than one host of more or less close relationship. These species are as 

 follows : Proteocephalus amhloplitis, P. cernuae, P. exiguus, P. filicollis, 

 P. longicollis, P. macrocephalus, P. percae, P. perplexus, P. pinguis, 

 P. pusillus, P. sulcatus, P. torulosus. In the following pages each of 

 these species is discussed separately. The hosts have been investigated 

 as to distribution and as to food habits in the hope that some clue might 

 be found to the relations existing between host and parasite, a relation 



