114 MR. F. J. MEGGITT ON A 
Gamble, F.R.S., for the very valuable help he has given me in 
the course of this work by his criticism and advice. My thanks 
are also due to Professor G. S. Brady for identifying specimens 
of Cyclops varius Lilljeborg submitted to him. 
ANATOMY. 
Historical. 
This species was first described by Rudolphi (21). He found 
two species of Cestodes, one in the intestine of Perca fluviatilis, 
and one in that of Gasterosteus aculeatus, and called them Tenia 
ocellata and T' filicollis respectively. In his original descriptions 
there is very little to distinguish between the two species. 
Early investigators, Bellingham (1), Dujardin (8), Diesing (7), 
and Cobbold (6), confined themselves to external characters, 
Zschokke (26) being the first to describe the internal anatomy. 
Later, Kraemer (10) made an exhaustive study of the two species, 
and concluded that there was no essential difference between them: 
in the same paper he gave a number of characteristics peculiar to 
fish Teenie, and suggested that they might form a special group. 
Still later, Lénnberg (15) separated them under the generic name 
of Ichthyotenia. Riggenbach (20), for the first time, summarised 
the investigations on the genus and added several new species to 
the list. In 1899, Railliet (19) showed that Tenia ambigua Duj. is 
synonymous with 7’. ocellata Rud. and 7’ filicollis Rud., and that 
therefore the genus Proteocephalus Wein. (25) is synonymous 
with Jchthyotenia: the first bemg the older name, should be 
adopted according to him. Benedict (3), who confirmed Kraemer’s 
description and elucidated a few fresh points, adopted this name. 
The latest paper upon the subject is that by La Rue (12). He 
asserts that Tenia filicollis Rud. and 7. ocellata Rud. are two 
separate species. The species which Kraemer described under these 
names, La Rue asserts was not 7’. filicollis nor 7. ocellata but an 
entirely new species (P. fallax La Rue). He further says that 
Benedict did not describe either of Rudolphi’s species, the species 
actually described being P. exigwus La Rue. Zschokke (26) also, 
according to him, described P. dubius La Rue, not 7. filicollis 
Rud. 
Tetracotylus (Monticelli, 18) he does not consider to be 
synonymous with Jchthyotenia. He adopts the generic name 
Proteocephalus on account of its priority : “I cannot regard the 
objections of Lithe (16) as adequate for its rejection.” This 
paper is merely a preliminary note to a monograph he is about 
to publish. 
From the brief historical account just given, it is obvious 
that the nomenclature of the group is in a state of great con- 
fusion. This is chiefly due to the vague descriptions of the 
early investigators, most of them being based upon characters, 
such as the scolex, which ave far too variable to be utilised for 
