88 ILLINOIS BIOLOGICAL MONOGRAPHS [88 



this species in Acerina cernua but the writer has not been able to find 

 any reference to this catch in any of Liihe's papers. Von Ratz (1897: 

 162) names Ichthyotaenia ocellata (Rud.) and /. filicollis (Rud.) as 

 parasites of Acerina cernua Linn, and I filicollis (Rud.) as a parasite 

 of A. schraetzer Cuv. in Lake Balaton. Since he gives no description a 

 determination of the systematic position of his specimens cannot be 

 made. They may belong to P. cernuae and they probably do not be- 

 long to P. percae (Miiller). Miihling (1898:17) stated that Ichthyo- 

 taenia ocellata had been found in East Prussia by Liihe. La Rue (1911: 

 475-476) described briefly P. cernuae from specimens used in the pres- 

 ent description. 



Von Siebold's and Liihe's specimens were collected in Prussia, the 

 same general locality as those of Braun which the writer has had for 

 study. For this reason and for the reason that they came from the 

 same host species it is deemed probable that they belong to the same 

 species. The specimens collected by von Ratz were taken from hosts 

 occurring in a different drainage system and may or may not belong to 

 P. cernuae. They probably do not belong to P. percae which comes 

 from the same general region, as does P. cernuae and which seems to be 

 limited to Perca fiuviatilis as a host. It is possible, of course, that they 

 represent a new species. With these possibilities in mind von Ratz's 

 specimens should be compared with parasites from Perca fiuviatilis and 

 Acerina cernua taken in Prussia or Finland. 



The description of this species is based on five specimens which 

 Prof. H. B. Ward secured from Prof. Max. Braun. The material bears 

 the label ' ^ Proteocephalus ocellata Rud. int. Acerina cernua L. Konigs- 

 berg, Pr, 8/93." These specimens bearing the number 09.26 and slides 

 of the same are now to be found in Professor Ward's collection. 



In general appearance these worms are short and robust. Four of 

 them are very short, 10.0-19.5-22.0 mm. The fifth measured about 40 

 mm. Yet each strobila has proglottids with ripe eggs. A maximum 

 breadth of 1.50 mm. was observed in the longest specimen and a breadth 

 of 1.309 mm. in a shorter one. The head (Figs. 5, 6) is not well set 

 off from the neck. Indeed, it is continuous with the neck which in all 

 five specimens is broader than the head. The anterior face of the head 

 is flattened and the suckers (Figs. 5, 6) are set at the margin of the 

 flattened area. They are small and not prominent and are directed 

 anteriad. No furrows or ridges mark the head. A fifth sucker is very 

 faintly visible. The head is 0.291-0,316 mm. broad at a point a little 

 posterior to the suckers. It is flattened dorsoventrally. Its length 

 which cannot be determined with any accuracy is about 0.100 mm. 



