112 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



have been able to icier some of them to species described by Leidy and others; some 

 agree superficially with Agamonema communis for example, but upon closer examina- 

 tion will be found to be covered by a thin investment which itself bears the distin- 

 guishing characters of Agamonema, while within this investment is a nematode which 

 is plainly a rudimentary Ascaris. 



Again, I have found specifically identical forms encysted in the body-cavity and 

 free in the intestine of the same fish. For example I found Dacnitis globosa Duj. 

 frequent in the alimentary canal, in the vicinity of the pyloric cceca, and the same 

 species in pediculated cysts in the body-cavity of the same fish, ISalmo myitis*. Special 

 attention should be given to these encapsuled, encysted, and immature nematodes. 

 The investigations should be made to cover as many months of the year as possible, 

 and attention should be given to details of structure, since the immature stages of 

 this order have few distinguishing features that can be made use of in classification. 



Another nematode, which I have collected a few times, shows such a remarkable 

 difference between the young and the adult as to call for special study. This is a 

 filaria of considerable length which I have found on the ovaries of Pomatomus salta- 

 trix and of Lobotes surinamensis, a description of which will be given in a forthcoming 

 paper. I have received the same worm in a collection of entoza from the United 

 States National Museum. The host in this case was Megalops thrissoides. This worm 

 grows to great length. One specimen from Lobotes measured 580 millimeters. The 

 aggregate length of the fragments from Megalops was over 3 meters, the diameter 

 about 1 millimeter throughout. The adult worm is bluntly rounded anteriorly and 

 tapers to a blunt point posteriorly. It is viviparous and contains, on account of its 

 great length and the small size of the young, from 0.2 to 0.36 millimeter in length, 

 an enormous number of g young. The latter are somewhat long clavate in shape, 

 thickest posteriorly, bluntly rounded at posterior end, while anteriorly for about one- 

 third of the entire length they taper to an exceedingly minute, attenuate point. The 

 young thus resemble the genus Trichosoma in outline. Whether these young filaria' 

 make their escape from the parent and penetrate the tissues of the host, or whether 

 they must await the ingestion of their host by some other animal before they are lib- 

 erated to begin a new life, I do not know. It is certain, whatever their ultimate fate 

 may be, that no one would suspect them of being the young of the filaria which gave 

 them birth if they had not been seen in the uterus of the parent. 



Lastly a very careful examination of the invertebrate food of fishes for larval para- 

 sitic forms should be made, so as to be able at last to determine the intermediate 

 host or hosts of all the known adult forms. 



It is not at all unlikely that some practical results would follow such investiga- 

 tions. 



Washington and Jefferson College, 



October 7, 1893. 



