135] PR0TE0CEPHAL1DAE—LA RUE 135 



Proglottidi prime corte e ottuse, le seguenti subquadrate. Aperture genitali irrego- 

 larmente alterne ; pene corto, sottilissimo, pendente, con una strozzatura verso 

 l'apice. Uova con due invogli, lunghe 0.089 mm - Rara nell' intestino dell' An- 

 guilla vulgaris (Trieste)." 



Stossich was evidently describing P. macrocephalus and not the P. 

 hemisphaericus (Molin). Miihling (1898:37, 69) noted this parasite in 

 A. vulgaris in East Prussia but gave no description. Schneider (1903: 

 29) reported from an eel a single specimen of what he then identified 

 as Ichthyotaenia hemisphaerica. Later in a footnote (1905:10) he says; 

 of these specimens "Ichthyotaenia hemisphaerica kommt, wie es scheint, 

 in den Aalen des Finnischen Meerbusens garnicht vor. Das Exemplar 

 welches ich fruher einmal irrtiimlich als /. hemisphaerica bestimmt habe 

 (Beitrage zur Kenntnis der Helminthenfauna des Finnischen Meerbu- 

 sens. Acta Soc. pro Fauna et Flora Fennica 26, No. 3. 1903. S. 29) , 

 erwies sich bei genauerer Unterschung audi als Ichthyotaenia macro- 

 cephala.^ 



From this statement the writer infers that Schneider at that time 

 considered P. hemisphaericus to be a distinct species. In the text of the 

 same article Schneider (1905:17-19) described P. macrocephalus, re- 

 cording for the first time in the history of the species a careful study 

 of its inner anatomy. For this reason a condensed resume of his de- 

 scription is here given. 



Proteocephalus macrocephalus: This species is a close relative of 

 P. percae and is differentiated therefrom by the very short cirrus-pouch 

 and the short cirrus. The scolex has a diameter of about 0.30 mm. The 

 diameter of the large deep suckers is 0.100 mm. The fifth sucker as in 

 P. percae is a rudimentary structure made up of long cells and having 

 a diameter of 0.025 mm. (The writer has shown that this organ in 

 P. percae is a true sucker.) The neck is quite broad and is strongly 

 compressed dorsoventrally. The body attains a length 40 cm. and more. 

 A specimen 11 cm. long and 1.8 mm. broad had about 200 segments. 

 The youngest proglottids are about five times as broad as long. The 

 middle mature proglottids are broader than long while ripe proglottids 

 are longer than broad. 



The ovaries appear from the surface as two small stripes, as they 

 do in P. percae. In old ripe proglottids they are of irregular shape, 

 bent and somewhat overlapped. The cirrus and vagina open irregu- 

 larly, alternating right and left, in the middle or a little anterior to the 

 middle of the proglottid margin. The cirrus-sheath scarcely equals Yq 

 the proglottid breadth, often much less. The ductus ejaculatorius 

 (cirrus-canal) forms some convolutions in the proximal end of the 

 cirrus-sheath and here widens out into a vesicula seminalis, 0.030 mm. 



