220 ILLINOIS BIOLOGICAL MONOGRAPHS [508 



EXPLANATION OF PLATE 



Fig. 59. Boihriocephalus scorpii, outline of mature segments. 



Fig. 60. Boihriocephalus scorpii, toto of same specimen. 



Fig. 6L Boihriocephalus scorpii, portion of strobila showing excretory vessels. 



Fig. 62. Boihriocephalus manubriformis, anterior primary segment. 



Fig. 63. Abolhrium rugosum, terminal excretory vesicle. 



Fig. 64. Abolhrium crassum, anterior segments of strobila from Coregonus clupeiformis, toto. 



