104 



ILLINOIS BIOLOGICAL MONOGRAPHS 



1384 



EXPLAXATIOX OF PLATE 



Fig. 45- 



Suckers and Hooks of Various Species of Polystomes 

 Polystoiim orbiculurc. bothriuiii from caudal disc. X 140. 

 Polystoiiia orbicularc, frontal section thru botlirinm. X 140. 

 PolystoiiH} obknlare, optical section of bothrinni showing cuticnlar 



framework. X 140. 

 ' Polystonta ol^acttiii, hook from base of sucker. X 165. 

 Polystoina oparnn:, hook from anterior margin of caudal disc. X 165. 

 Polysloina tr.iirocotylc, hooks of posterior margin of disc. X 165. 

 Polystoina o/'acii:}:. hooks of posterior margin of disc. X 165. 

 Polystoina ir.cgacotylc, hooks of posterior margin of disc. X 165. 

 Polystoina coronatuiii, hooks of posterior margin of disc. X 165. 

 Polystoina orbicularc, hook from base of sucker. X 165. 

 Polystoina orbicularc. frontal section thru a sucker illustrating the method 



of operation; the e.xtcrnal zones are retracted with the resulting 



protrusion of the basal part. X 140. 

 Polystonia intcgerriiiiuiu. frontal section thru a sucker sliowing type of 



cuticnlar framework. Compare with text and types illustrated in 



other figures. X 100. 



