No. 2194. NORTn AMERICAN PARASITIC COPEPODS— WILSON. 109 



and neck of the Pennella tire frequently twisted in corkscrew fashion, 

 thereby increasing the difficulty of withdrawing them and givijig 

 the copepod a more secure hold upon its host. These cysts may bo 

 found almost anywhere in the fish's body, in the stomach and intes- 

 tine walls, the mesentery, the liver, the caeca, etc. When the copepod 

 dies the cyst simply shrivels and hardens still more, and such lumps, 

 nearly as hard as bone, may be cut out of the liver or elsewhere along- 

 side of the living ones. 



The portion of the parasite which hangs free in the water outside 

 the fish's skin is frequently infested with goose barnacles, hydroids, 

 or algae. One specimen was obtained, 4 inches in length, to which 

 were attached 18 Conchoderma virgatum, the mass of the barnacles 

 being many times that of the copepod's body. 



Quite recently {1912b) Quidor has published a paper on copepod 

 parasites, in which he gave a diagnosis of the genus Pennella and 

 then discussed its life history and specific characters. After show- 

 ing that various other data did not furnish favorable specific char- 

 acters, he advocated the structure of the plumose abdominal ap- 

 pendages and the individual torsion as a ready and infallible means 

 of distinguishing species (pp. 202-3). 



The structure of the abdominal appendages was quite thoroughly 

 discussed by Steenstrup and Liitken in connection with Pennella 

 Hagitta. 



While it may be possible to select plumules from the different 

 species Avhicb will show the distinctions portrayed by Quidor, it is 

 also possible to find on the same fish two Pennellas of the same species, 

 fastened side by side, but whose plumules show very different struc- 

 ture. So long as this is likely to occur it is evident that something 

 else must be used to separate the species. With reference to the value 

 of torsion, if Quidor'? observations were based upon the statements 

 contained in his description of the genus, they must be profoundly 

 modified before they will possess any scientific value. He stated: 

 "La tete . . . presente ventralment deux antennes rudimentaires et 

 une region buccale couverte d'appendices chitineux plus ou moins 

 ramifies" (p. 197); and, again: "II (the genital segment) porteen 

 arriere, sur la face dorsale, les orifices de ponte d'on sortent deux 

 longs sacs ovigieres filiformes." (P. 198.) 



The two pairs of antennae are dorsal and not ventral, and the egg 

 strings are ventral and not dorsal, as in every Lernaeid genus. By 

 placing the antennae with the mouth on the ventral surface Quidor 

 Is reduced to the unhappy situation of calling the swimming legs 

 dorsal, since they are on the opposite surface. 



As a consequence all the torsion which he called direct is really 

 inverse and his inverse torsion is really direct, because he was hold- 



