56 ILLINOIS BIOLOGICAL MONOGRAPHS [56 



of killing. The maximum breadth found by the writer varied from 

 0.425-0.595-0.646 mm. while Benedict records a maximum of 0.8 mm. 

 The globular head according to Benedict is 0.120 mm. broad. The 

 writer found it to be 0.148-0.160-0.170 mm. broad. The suckers placed 

 just above the broadest zone are directed slightly anteriad. They are 

 0.069-0.085 mm. long by 0.058 mm. broad with an opening of 0.042-0.048 

 mm. by 0.027-0.032 mm. Benedict states that the sucker is 0.040 mm. 

 in diameter, but it seems that he must mean the diameter of the opening 

 and not the diameter over the whole sucker. A fifth sucker is present, 

 0.037-0.048 mm. in diameter. This from toto preparations is appar- 

 ently a true sucker. Benedict says it has the "same structure and 

 musculature that the four large suckers possess." His drawing of the 

 head is reproduced (Fig. 138). 



The neck measures 2-4 mm. in length by 0.110-0.120 mm. broad. 

 Benedict found the neck to be 5-10 mm. long by 0.10-0.20 mm. broad. 

 The neck passes over into the first proglottids almost imperceptibly. 

 The first proglottids are longer than broad or nearly quadrate. These 

 very immature proglottids are few in number. The anlage of the 

 genital organs appear very early and in proglottids a little further back 

 mature sexual organs appear. Mature proglottids are longer than broad 

 and are few in number. Ripe proglottids are longer than broad. Three 

 of these measured 0.935 by 0.595 mm., 0.680 by 0.560 mm., 1.190 by 

 0.460 mm. Ripe proglottids are considerably larger than the mature. 

 The increase in length, breadth and thickness is rapid. The longest 

 proglottid in the strobila is usually the last one and sometimes also it 

 is the broadest. Three terminal proglottids measured 1.190 by 0.646 

 mm., 0.714 by 0.51 mm., 1.50 by 0.40 mm., the length being stated first. 

 The end proglottid is variable in form and functional. It usually 

 tapers to a blunt point at its posterior end where the excretory pore is 

 situated. The segmentation is not evident. The angles at the ends of 

 the proglottids are scarcely marked and the intersegmental furrows are 

 shallow. The total number of proglottids in a strobila is small, 10-12- 

 14-15-20. Benedict found one specimen with 40 segments. 



Benedict's findings on points of histology are probably correct and 

 have not been checked over. The common genital sinus is situated 

 near the middle of the margin of the proglottid, usually slightly ante- 

 rior thereto. It alternates irregularly. 



The testes (Fig. 50) are 37-50-54 in number, 35-50 according 

 to Benedict. They measure 0.040-0.045-0.050 mm. in diameter. The 

 testes lie in a single layer between the vitellaria and anterior to the 

 ovary. In toto mounts the writer could not make out with certainty the 

 coils of the vas deferens yet they seemed to lie in the middle of the 



