136 ILLINOIS BIOLOGICAL MONOGRAPHS [136 



in diameter. The convolutions of the vas deferens outside of the cirrus- 

 sheath are excentric on the porose side. In other species with a long 

 cirrus-sheath this convoluted mass lies in the middle of the proglottid. 

 The vagina is provided with a small sphincter muscle close to the 

 vaginal opening. Without broadening out into a receptaculum seminis 

 the vagina passes into the ovarial region. The oocapt is very muscular. 

 The uterine passage measures 0.02 mm. in diameter and the vitelline 

 reservoir, 0.30 mm. The vitellaria are voluminous and follicular. The 

 opening of the uterine passage and the well preformed uterine opening 

 on the ventral side are found almost in the same transverse section 

 posterior to the middle of the proglottid. The uterus has about eight 

 branches on either side. Testes, numbering about 100 in each proglottid, 

 lie irregularly in one or two layers. They measure about 0.150 by 0.075 

 mm. Ventral excretory vessels measure about 0.009 mm. in diameter, 

 the dorsal vessels about 0.0025 mm. This species occurs only in An- 

 guilla vulgaris and only in small numbers. 



In this connection the writer thinks it of interest to note that 

 Creplin's specimens were taken at Greifswald in Prussia while Schnei- 

 der's were taken in Finland. Geographically these habitats are not 

 distant nor do any barriers exist to prevent the movement of the eels 

 from one locality to the other. For this reason and because of anatomi- 

 cal similarities it is extremely probable that Schneider's specimens were 

 of the same species as Creplin's. It is to be noted that Dujardin's 

 observations on the size of specimens taken from Anguilla vulgaris at 

 Rennes, France, agree very well with those which Schneider describes. 

 Nufer (1905) described and figured what he considered to be P. macro- 

 cephala (Creplin). He found two specimens in the intestinal tract of 

 a single Anguilla vulgaris from Lake Lucerne. Nufer shows such strik- 

 ing inconsistencies in his statements and these agree so poorly with the 

 findings of Schneider and the writer that it seems best to analyse parts 

 of his paper. Compare his description of the head (Nufer 1905:137) 

 and his statement about the head in his summary (Nufer 1905:145) 

 with the facts presented in tabular form on pp. 146-147 of his paper 

 where he compares P. macrocephalus, P. ocellatus, P. longicollis, and P. 

 torulosus. All of these species he reports from Lake Lucerne. 



He writes (page 137) : 



"Der Scolex ist sehr gross, ziemlich breit, rundlich, und besitzt einen Durch- 

 messer von 0.1512 mm. Gegen den Hals ist er scharf und deutlich abgesetzt und 

 iibertrifft alle iibrigcn i»i J r ierwaldstdttersec vorkommenden Proteocephalensco- 

 lices an Grosse um Bcdcutcndcs (The italics are mine, La Rue.), weshalb Creplin, 

 auch auf den Gedanken gekommen sein mag, diesen Proteocephalen mit "macro- 

 cephalus" zu bezeichnen. Vorne ist der Skolex mit vier grossen, runden Saug- 



