104 



ILLINOIS BIOLOGICAL MONOGRAPHS 



, 



[384 



EXPLANATION* OF PLATE 



'ig- 45- 



Suckers and Hooks or Various Species of Polystomes 

 Polystoma orbiculare, bothrium from caudal disc. X ~4°- 

 Polystoma orbiculare, frontal section thru bothrium. X 140. 

 Polystoma obiculare, optical section of bothrium showing cuticular 



framework. X 140. 

 Polystoma opacuni, hook from base of sucker. X 165. 

 Polystoma opacuni, hook from anterior margin of caudal disc. X 165. 

 Polystoma microcotyle, hooks of posterior margin of disc. X 165. 

 Polystoma opacuni, hooks of posterior margin of disc. X 165. 

 Polystoma megacotyle, hooks of posterior margin of disc. X 165. 

 Polystoma coronatum, hooks of posterior margin of disc. X 165. 

 Polystoma orbiculare, hook from base of sucker. X 165. 

 Polystoma orbiculare, frontal section thru a sucker illustrating the method 



of operation; the external zones are retracted with the resulting 



protrusion of the basal part. X 140. 

 Polystoma integerrimum, frontal section thru a sucker showing type of 



cuticular framework. Compare with text and types illustrated in 



other figures. X 100. 



