INTERNAL PARASITES OF THE SEBAGO SALMON. I 1 83 



Leidy has described (1851,9. 206) a form as Distomumterreticolle'^ Rudolphi, 

 which Pratt (1902, p. 957) lists as Azygia tereticollis (R.) Leidy. The original 

 description is as follows (Leidy, 1851, p. 206) : 



Distomum lerrelicoUe, Rud. Entoz. Syn., p. 102; Dujardin, Hist. Nat. des Helm.; 

 Diesing, Syst. Helm., p. 358. 



Body subcylindric, light flesh color, posteriorly rounded. \'entral acetabulum (^ 

 line) 1.6 mm. behind the oral ('3 line) 0.7 mm. in diameter. Oral acetabulum ('4 line) 

 0.5 mm. 



Length (8 lines) 16.8 mm.; breadth posteriorly {yi line) i mm., anteriorly i]-^ line) 

 0.7 mm. 



Habitation. — Stomach of Esox reticulatus Lesueur. 



Remark. — The generative aperture is placed immediately in advance of the ventral 

 acetabulum. When the animal contracts, the two acetabula are nearly brought into 

 contact. 



The description is scanty, and yet one can say with some assurance that the 

 form before I^eidy was not the European species named by Rudolphi and dis- 

 cussed by a long series of authors, of whom Looss (1894) has given the most 

 complete description with truly admirable figures. Leidy's specimen is much 

 too small for average adults of Azygia tereticollis, which is, moreover, cylindrical 

 instead of broader posteriorly, as was Leidy's worm. Again, Azygia tereticollis 

 has the oral sucker larger than the acetabulum, whereas in Leidy's form the 

 reverse is true. Finally the suckers in Leidy's form do not agree at all in .size 

 with the suckers in Azygia tereticollis, as described by Dujardin and others. 



It is somewhat more difficult to say whether the form before Leidy was the 

 same as that I collected in the Sebago salmon. In size the two are not very 

 different, although Leidy's was larger. Other measurements do not agree at 

 all well. The sizes given for the suckers are just about reversed. The final 

 determination of this point, however, must await a reexamination of Leidy's 

 original material. 



The only other reference to the occurrence of Azygia on this continent, so far 

 as I know, is the brief note of Stafford (1904, p. 488), in which he records Azygia ^ 

 tereticollis Rudolphi from mouth, pharynx, oesophagus, and stomach of Esox 

 lucius Linnaeus, Lota maculosa Le Sueur, and Ameiurus nigricans Le Sueur. 

 Absolutely the only data concerning the worm which Stafford records is the size, 

 12 by I mm. Now, this does not agree with adults of A. tereticollis, for Looss 

 (1894, p. 18) says of that species that the first eggs are not set free into the 

 uterus until the worm is 8 to 10 mm. or more in length, and these are uniformly 

 abnormal and defective. In another place he remarks (1894, p. 7) that in most 

 cases eggs are found in worms 12 mm. long, although in scanty numbers. I 

 am of the opinion that Stafford did not have before him the true A. tereticollis 



oThe text by error contains lerreticolle for the specific name instead of tereticoUe. 

 6 Unfortunately, Stafford spells the genus Azigia and the species tereticoUe. 



