128 ILLINOIS BIOLOGICAL MONOGRAPHS [128 



tending from the cirrus-pouch to the mid-field of the segment. Kramer 

 (Fig. 184) figures the coils of vas deferens lying in the middle of the 

 segment. The cirrus-pouch is short and relatively thick. Its length is 

 about 0.255 mm. and its breadth 0.085 mm. The ratio of its length to 

 the proglottid breadth is about 1 :4 according to G. Schneider, 1 -.3 in 

 Kraemer's drawing, and 1:4-1:6 in my preparations. The cirrus is 

 short and not very thick. Kraemer's description of the cirrus is faulty 

 in that he said that the cirrus was armed with recurved hooks which 

 extend back into the tissue of the cirrus itself. There are no hooks. 

 The protruded cirrus has not been seen by the writer. The ductus 

 ejaculatorius forms but a very few coils or instead of coils it may lie 

 in sinuous curves within the cirrus-pouch. 



The vagina which opens mostly dorsal to the cirrus-pouch has a 

 very weak sphincter muscle situated near the opening into the atrium. 

 This sphincter vaginae is made up of a few strands of circular muscle 

 fibers which may be easily overlooked. In its course to the interovarial 

 space the vagina does not cross the cirrus-pouch but passes dorsal and 

 anterior to the pouch. A small receptaculum seminis is present just 

 anterior to the ovary. The vitellaria are lateral, voluminous, and fol- 

 licular. The follicles are large and closely packed together. The bi- 

 lobed ovary is large, well developed, thick and irregular in outline, but 

 the lobes are not as slender as they are shown in Kraemer's figure 

 (compare Figs. 79 and 184). In proglottids 1.3 mm. broad the ovary 

 may have a span of 0.80 mm. and the lobes may be 0.130-0.140 mm. 

 thick. A muscular oocapt and an ootype are present. The uterus in 

 ripe proglottids has 3-4 lateral out-pocketings on either side. The ute- 

 rine pores have not been observed. The eggs were not described by 

 Kramer and Schneider. The outer membrane is thin and hyaline, 

 0.055 mm. in diameter. The granular second membrane has a diameter 

 of about 0.032 mm. and the embryo about 0.021 mm. A delicate mem- 

 brane closely invests the embryo. 



P. torulosus differs from many other species of the genus by its 

 large size, and from a large number of the species through its lack of a 

 fifth sucker. In maximum length and breadth of its strobila it is the 

 largest species of Proteocephalus yet described. In the width of the 

 head and diameter of the suckers it is exceeded only by P. ambloplitis 

 and P. perplexus. In observed length P. torulosus greatly exceeds these 

 species — and it may be differentiated from them by its lesser number 

 of uterine pouches, its weaker sphincter vaginae, its shorter cirrus- 

 pouch, its double layer of testes, and by the arrangement of the dorsal 

 layer of the same. It is greatly different from the other North Ameri- 

 can forms thus far described. Among the European forms P. torulosus 



