104 



ILLINOIS BIOLOGICAL MONOGRAPHS 



1384 



EXPLAXATIOX OF PLATE 



Fig. 45. 



Suckers .^xd Hooks of V.^8I0l•s Species of Polystomes 

 Polystotr.a orbiculare, bothriuin from caudal disc. X 140- 

 Polystoiiia orbiculare. frontal section thru bothrium. X 140. 

 Polystoitia obiculare, optical section of bothriuin showing cuticular 



framework. X 140. 

 ' Poly stoma opacum, hook from base of sucker. X 165. 

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

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

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

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

 Polystoma coroiiatuiii, 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 iittcgerrimum, frontal section thru a sucker showing type of 



cuticular framework. Compare with text and types illustrated in 



other figures. X 100. 



