206 



MARTIN 



The number of unidentified infections was highest in February and 

 lowest in October. February's high probably is a reflection of the recent 

 heavy exposure of the snails to infective stages of the trematodes resulting 

 when the bird population is increased by migratory species. 



Figure II 



In the infection numbers listed in Table I are included 667 double 

 and 23 triple infections. The seasonal distribution of double infections is 

 shown in Figure II. 



Certain combinations of cercariae in double infections occurred much 

 more frequently than others. Table II lists the combinations in their 

 order of frequency. 



