8 University of Michigan 



elongated. As the proglottids get older and more elongated 

 the ovarian lobes are turned back and become rounded. In the 

 last proglottid this process has gone on so far that the ovarian 

 lobes touch in the rear. The six hooked embryos of uterine 

 eggs measure 0.015 to 0.017 mm. 



One complete worm taken by the writer from perch at 

 Douglas Lake in northern Michigan dififers very little from 

 the type. It is strongly contracted. The suckers, which are 

 almost withdrawn into the head, are about 0.066 mm. in diamet- 

 er. The fifth sucker is just distinguishable. The neck is broad 

 and about 1.30 mm. long. Two headless fragments mounted 

 on the same slide clearly belong to the same species as the 

 type. 



A complete specimen, La Rue's No. 357e, 134 nim. long 

 and with a maximum width of 0.50 mm., was taken from a rock 

 bass, Anibloplitcs rupcstris (Raf.), at Douglas Lake, Michigan, 

 by the writer in 19 12. Studies of this worm mounted in toto 

 show that it belongs in this species. Its measurements fall 

 within the limits given in the diagnosis. 



This species is much smaller than P. cernuae, P. percae, and 

 P. dubiiis which infest the Percidae of Europe but resembles 

 these in having a fifth sucker. In addition to differences in 

 size of the worm there are many points of difiference in the 

 size of organs. This species is considerably smaller than P. 

 pingnis. It is less fleshy and dilTers in many of its size rela- 

 tions. It somewhat resembles P. exiguns in size but is a 

 slightly more robust worm than P. exigmis. This more robust 

 appearance is particularly true of the head and neck. The 

 genital pore of P. pcarsci is differently located, the cirrus-pouch 

 much smaller, testes more numerous, and the embryo smaller 

 thin in P. exiguns. The form more closely resembles P. 

 pusillns than any other described species, but its suckers are 



