216 ILLINOIS BIOLOGICAL MONOGRAPHS [216 



glottids in this region are 1.275 mm. broad by 0.30-0.40 mm. long. 

 Mature proglottids are about 0.85-1.0 mm. square, or they may be longer 

 than broad. Some of the elongated proglottids measure 2.5 mm. long 

 by 0.45-0.5 mm. broad. In Fuhrmann's specimens the last proglottids 

 were 0.7 mm. long by 1.35 mm. broad. Neither Fuhrmann nor the 

 writer has seen the ripe proglottids. All the hosts examined by the 

 latter had been in captivity for some time and were examined in the 

 spring months. It may be that the parasites attain the sexually ripe 

 condition later in the season. 



The excretory system (Fig. 189) is made up of two pairs of main 

 lateral vessels, dorsal and ventral. These are situated much farther 

 mesad than is usually the case with this group. They take a spiral 

 path through the tissues. From them at frequent intervals small 

 branches pass to the dorsal and ventral surfaces. A transverse excre- 

 tory commissure is present in the posterior part of each segment. In 

 the head the main excretory vessels are connected by means of many 

 anastomosing branches. The parenchyma resembles that of 0. fila- 

 roides. Chalkbodies of large size are abundant, especially in the head 

 and neck. The musculature is weakly developed. 



The genital pore alternates irregularly, is marginal, and is situated 

 at the end of the first third or two-fifths of the proglottid. Cirrus- 

 pouch and vagina pass to the exterior between the ventral and the 

 dorsal excretory vessels. The male organs mature first. Testes number 

 from 90 to 160, the number varying greatly in the proglottids of the 

 same strobila. Elongated testes measure 0.05-0.08 and even as much as 

 0.120 mm. in maximum dimension. The testes (Fig. 189) lie in two 

 broad fields which extend laterad and mesad of the excretory vessels. 

 In many proglottids an occasional testis lies in the midfield. The testes 

 are dorsal to the uterus. In mature proglottids the vas deferens forms 

 a large mass of coils which function as a vesicula seminalis. This mass 

 of coils is usually situated posterior to the cirrus-pouch. It lies almost 

 in the mid-field of the segment. The cirrus-pouch is short and broad. 

 Its length varies from 0.185 to 0.290 mm. and its breadth from 0.050 in 

 the case of the long slender pouches to 0.085-0.100 mm. in the shorter 

 and thicker pouches. The cirrus-sheath is broadest at the inner end. 

 The ductus ejaculatorius forms several coils and then it passes over into 

 the slender cirrus. In some proglottids the ductus is dilated to form a 

 small vesicle. The cirrus is not muscular. When protruded it is cylin- 

 drical and about 0.13-0.15 mm. long by 0.045-0.050 mm. thick. There 

 are no coils of ductus ejaculatorius in the base of the protruded cirrus. 



The vagina lies anterior or posterior to the cirrus-pouch but its 

 opening is usually dorsal to the latter. When the vagina occupies the 



