220 ILLINOIS BIOLOGICAL MONOGRAPHS [508 



EXPLANATION OF PLATE 



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



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



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



Fig. 62. Bolhriocephalus manubriformis, anterior primary segment. 



Fig. 63. Abolhrium rugosum, terminal excretory vesicle. 



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



