99] PROTEOCEPHALIDAE — LA RUE 99 



Schneider (1902:21-22) reported a species of cestode parasitic in 

 Perca fluviatilis which he considered to be Ichthyotaenia filicollis. He 

 believed this to belong to the species found by Zschokke (1884) in the 

 same host species. He noted the fact that Kraemer (1892) considering 

 his Taenia filicollis to be a younger stage of Taenia ocellata, put his 

 two forms together in the same species, T. ocellata. To this last 

 Schneider did not agree but held that the specimens from Perca fluvi- 

 atilis and Coregonus lavaretus were distinct species. He noted on the 

 one hand the near relationships and the great similarities of the species 

 of the Ichthyotaenia and on the other extreme variability of the cestodes. 

 He concluded that it was not therefore wholly unlikely that the one 

 form stands in relation to the other as a variety which has arisen from 

 the changed environmental conditions of the new host. He further gave 

 a short description of the worm in which he considered external charac- 

 ters almost exclusively. In the same article Schneider ( 1902 :23 ) re- 

 ported some specimens of Ichthyotaenia ocellata from Coregonus 

 lavaretus and from Cottus quadricornis. It seems improbable that the 

 latter species is a host of the cestode mentioned. 



Schneider (1903:13-23) decided to avoid entirely the questions of 

 identity surrounding the names Taenia ocellata and Taenia filicollis Rud. 

 He proposed to use the older name Taenia percae to designate that form 

 from Perca fluviatilis which he (1902:21-22) had previously considered 

 to be Taenia filicollis Rud. His reasons for this action need not be 

 stated here. As synonyms of Ichthyotaenia percae he cited Taenia 

 percae Muller (1788:5, pi. XLIV), Taenia ocellata Rudolphi (1810:108), 

 Taenia filicollis Zschokke (1884:16-18) in part, Ichthyotaenia ocellata 

 Riggenbach (1896:268) in part, and Ichthyotaenia filicollis Schneider 

 (1902:21) in part. It is to be noted that Schneider failed to include 

 in his synonymy any part of Kraemer 's (1892) Taenia ocellata. This 

 seems the more remarkable when it is remembered that both Kraemer 

 and Riggenbach were students under Zschokke and it is quite likely 

 that both the pupils accepted the determination of their master on the 

 latter 's T. filicollis. Nevertheless parts of Zschokke 's and Riggenbach 's 

 data on T. filicollis are held to apply to Ichthyotaenia percae. Nor did 

 Schneider refer to Benedict (1900) in his synonymy. In this he was 

 correct for in another part of this work it is shown that Benedict 

 was working on a distinct species for which La Rue (1911) has pro- 

 posed the name Proteocephalus exiguus. In his later description of the 

 species Schneider (1905) gave nothing further on the synonymy of 

 Ichthyotaenia percae but he added some descriptive data to that given 

 in his papers of 1902 and 1903. 



Luhe (1909) considered Taenia ocellata Rud. a synonym of Ichthyo- 

 taenia percae (O. F. Muller). In his diagnosis he followed Kraemer 



