57] PROTEOCEPHALIDAE — LA RUE 57 



proglottid near the dorsal wall. Benedict figures the vas deferens as 

 forming a coil extending beyond the middle of the segment. The 

 cirrus-pouch (Figs. 50, 51, 52) is elongated, slightly broader near its 

 inner extremity and slightly constricted near the middle. It reaches 

 the middle of the segment or even beyond that point in mature pro- 

 glottids. Its length increases with the maturity of the segment. The 

 following measurements of its length were taken from successive pro- 

 glottids, 0.289, 0.296, 0.313, 0.330, 0.341 mm. the last being the maxi- 

 mum length found. The unprotruded cirrus is straight. The writer 

 has not seen it evaginated. According to Benedict the evaginated cirrus 

 extends 0.10 mm. from the male opening. The ductus ejaculatorius is 

 straight. 



The vagina (Figs. 50, 51, 52) opens into the common genital sinus 

 and it always lies anterior to the cirrus-pouch. In a single proglottid 

 the vagina was found posterior to the cirrus-pouch. This is probably 

 to be considered as an abnormality or a very rare variation. A weak 

 sphincter vaginae occurs a short distance from the vaginal opening. 

 This sphincter is 0.008 mm. thick and is circular in cross section (Bene- 

 dict). As Benedict has described it, the vagina extends straight in for 

 a short distance then it "bends backward and inward passing under 

 the middle of the cirrus-sac". The ovary very much resembles that of 

 P.fallax (Kraemer's Taenia ocellata) in shape. The lobes are thick and 

 solid. Benedict's comparison of their shape to that of a retort is excel- 

 lent. The ovary is early decadent. The relations of the organs of the 

 interovarial space are typical of the genus as Benedict has described 

 them. The vitellaria are follicular. The follicles are not large nor are 

 they closely packed. They too are decadent early. The uterus (Figs. 

 51, 52) in ripe proglottids consists of a median tube and 9-14 lateral 

 pouches on either side. These pouches occupy the ventral part of the 

 segment while the testes are dorsal. "The eggs which are found in 

 the uterus have a diameter of 0.02 mm." (Benedict). Measurements 

 by the writer gave a range of 0.019-0.021 mm. for the embryo and 

 0.036-0.046 mm. for the second membrane. The outer membrane meas- 

 ures 0.038-0.060 mm. The second membrane is thick and granular while 

 the outer membrane in uterine eggs is thick and hyaline. 



This species somewhat resembles P. pusillus Ward but is differenti- 

 ated from that species by the smaller size of its head, by its very much, 

 smaller suckers and smaller sucker openings. This species has a much 

 longer neck than has P. pusillus. The character of the segmentation of 

 the two worms is utterly different being very evident in P. pusillus r 

 with deep constrictions between proglottids. In P. exiguus segmenta- 

 tion is not evident. The number of proglottids in P. pusillus is greater 



