206 ILLINOIS BIOLOGICAL MONOGRAPHS [206 



However some of them appear nearly triangular. They measure 0.105- 

 0.170 mm. in diameter. In the smaller ones the effect of contraction 

 is very plainly shown by the deeper cavity and by the thickened muscu- 

 lar wall. The diameter of the sucker opening varies from 0.053 to 

 0.105 mm. A vestigial fifth sucker resembling that of 0. filaroides is 

 found imbedded in the tissues of the head. The neck is always long, 

 5 to 7 mm., and its breadth is subject to considerable variation, from 

 0.170 to 0.425 mm. 



Since this study is based upon toto preparations almost exclusively, 

 the excretory, nervous and muscular systems were not studied carefully. 

 The excretory system is made up of coiling trunks and anastomosing 

 branches in the head and extreme anterior neck region. In the pro- 

 glottids two pairs of main lateral excretory vessels can be made out. 



The sexual organs (Fig. 102) in their character and relations are 

 typical of the snake Proteocephalids. The genital sinus is marginal, 

 irregularly alternating and situated near the middle, or it may be as 

 far anterior as the end of the first % of the proglottid. It is marked 

 by a slight elevation which becomes more pronounced in the more elon- 

 gated proglottids. The vagina and cirrus open into the common shallow 

 genital sinus. The vagina lies either anterior or posterior to the cirrus- 

 pouch but more frequently anterior. Rarely the vagina is dorsal to the 

 cirrus-sheath. 



The testes are very numerous, 150-215. They are arranged in two 

 fields, leaving a free median zone. In elongated mature and ripe pro- 

 glottids the testes are oval or even polygonal. They measure as much 

 as 0.053 by 0.106 mm. It is to be noted that the testes tend to occur in 

 groups of 2, 3 or 4. In these cases the limiting membranes of the testes 

 touch each other. The vasa efferentia may be clearly seen in some toto 

 preparations. They much resemble the vasa efferentia in other species. 

 The vas deferens in young proglottids is nearly straight. It arises in 

 the middle of the proglottid and extends to the cirrus-pouch which it 

 enters. As the proglottid becomes older the vas deferens becomes longer 

 and more and more coiled until in mature and ripe proglottids it forms 

 a heavy mass of colls lying between the cirrus-pouch and the middle of 

 the segment. When filled with deeply stained spermatozoa this mass 

 becomes very prominent. Upon entering the cirrus-pouch the vas 

 deferens becomes the ductus ejaculatorius, which is coiled several times 

 before passing over into the heavier-walled cirrus. The cirrus is some- 

 what swollen but is much smaller than in Crepidohothrium gerrardii, 

 0. calmettei, or 0. grandis. When protruded it is slender and of even 

 diameter from tip to base. Its length protruded is about 0.200 mm. 

 This measurement is taken from a specimen from Oklahoma. The 



