139] PROTEOCEPHALIDAE—LA RUE 139 



simulated almost exactly. Likewise in the position of the mass of coils 

 of the vas deferens, in the number, size and arrangement of the testes 

 Nufer's description and his tabulated data (p. 146) agree very well 

 with the writer's drawing and description of the same organs in P. fal- 

 lax La Rue. His description of the male organs of the species in ques- 

 tion cannot be said to agree with the writer's drawing (Fig. 49) which 

 is a delineation of the proglottid of P. macrocephalus. Nor does his 

 description agree with Schneider's or my own description of the pro- 

 glottid of that species. 



Unfortunately the writer has not had the opportunity of examining 

 Nufer's material of this species nor any other specimens of cestodes 

 taken from the eels of Lake Lucerne. He cannot therefore make a 

 positive determination of Nufer's form. The evidence at hand permits 

 several interpretations. These are : 1, that Nufer permitted his cestode 

 material from Anguilla to become confused with specimens of P. fallax 

 from Coregonus fera; 2, that the Anguilla of Lake Lucerne harbor P. 

 fallax; 3, that the ripe proglottids described by Nufer had been taken 

 into the intestine of the eel with its food, perhaps Cor eg onus fera, liv- 

 ing or dead. Supposition 1 is always a possibility when one is 

 working with such material. Supposition 2 does not give complete 

 satisfaction because if the eels of Lake Lucerne harbor P. fallax Nufer 

 ought to have been able to find a fifth sucker, which he failed to do. 

 The third supposition permits one to consider that Nufer's whole speci- 

 mens were really P. macrocephalus but that the ripe proglottids (in 

 reality from P. fallax) upon which he based his description of the pro- 

 glottids became confused with the specimens of P. macrocephalus by 

 natural means. The embryo of Nufer's form is about the size of the 

 embryo of P. macrocephalus as determined by the writer. His meas- 

 urement of the embryo was 0.0184 mm. while the embryos of the writer's 

 specimens of P. macrocephalus measured 0.017-0.019 mm. and rarely as 

 much as 0.021 mm. in an elongated embryo. The embryo of P. fallax 

 is much larger, according to the writer's measurements being 0.0312- 

 0.0336 mm. in diameter. 



Thus far attention has not been called to Nufer's description of 

 the female generative organs. He claims that the histological structure 

 of the vaginae of P. macrocephalus and of P. ocellatus differs in some 

 respects. The writer's own investigation of the two species, especially 

 when the investigations of Kramer are taken into consideration, lead 

 him to believe that the vaginae of the two species are much alike in 

 histological detail. Nufer describes the ovary as being single, not bi- 

 lobed. In this he has been led astray by a condition sometimes found 

 in ripe end-proglottids. In such cases the lobes of the ovary may be 



