62 ILLINOIS BIOLOGICAL MONOGRAPHS [62 



cient material but very few sections have been made and these were too 

 poor to yield much valuable data. 



The vagina (Figs. 54, 55) usually opens anterior and dorsal to the 

 cirrus-pouch but rarely (Fig. 53) it is posterior to the same. The 

 number of proglottids examined have been too few to establish whether 

 the posterior position of the vagina is normal. Even when in the ante- 

 rior situation the vagina does not cross the cirrus-pouch. From its 

 opening it makes a long curve toward the middle of the proglottid 

 which it reaches at a point posterior to the inner end of the cirrus- 

 pouch. The vagina is dorsal to the uterus. A vaginal sphincter could 

 not be demonstrated, and if present it must be very weak. The pres- 

 ence of a receptaculum seminis has not been demonstrated. The bilobed 

 ovary (Figs. 53, 54, 55) is peculiar in that the lobes which are short and 

 very thick are pressed closely together. This is a condition not yet 

 found regularly in any other species of the genus altho Nufer (1905) 

 found it in P. macrocephalus. In transverse sections the thickness and 

 compactness of the ovary are noted at once. The vitellaria are sparse, 

 the follicles small. The ducts of the interovarial space have not been 

 thoroly investigated. An ootype and an oocapt are present. 



In ripe ploglottids the uterus (Fig. 53) shows 10-14-16 lateral out- 

 pocketings on either side. No uterine pores have been seen. The eggs 

 have not been observed. 



Other specimens which the writer has provisionally assigned to this 

 species were taken by Dr. H. B. Ward from the pyloric and intestinal 

 regions of Cristivomer namaycush Walbaum (?), Lake Temagami, On- 

 tario, August, 1910. It seems that the determination of the host must 

 remain somewhat in doubt for there was no attempt at the identification 

 of the fish when it was caught and it was not preserved. The identifica- 

 tion was made from the memory of the appearance of the fish after the 

 return of the expedition. Both Professor Reighard and Professor 

 Ward when questioned by the writer thought there could be little doubt 

 of the determination. These specimens bear the lot numbers Tip, Tlj, 

 T2h, and T2p in Dr. H. B. Ward's collection. 



The specimens are small, measuring up to 20-30 mm. long. No 

 specimens have ripe proglottids. When the worm is fully mature it is 

 perhaps considerably longer. Measurements of a number of specimens 

 yielded the following data : Average breadth of seven heads 0.284 mm., 

 maximum breadth of same 0.340 mm., minimum 0.244 mm. ; average 

 length of six heads 0.177 mm., maximum length of same 0.238 mm., min- 

 imum 0.133 mm. ; average length of seventeen suckers 0.134 mm., maxi- 

 mum length of same 0.179 mm., minimum 0.106 mm.; average breadth 

 of thirteen suckers 0.108 mm., maximum breadth of same 0.127 mm., 



