198 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



species. Often in a lot of encapsuled forms, collected at the same time from the same 

 host, individuals are obtained which differ very considerably one from another. 



One viviparous species belonging to the genus Ichthyoncma (which I have referred, 

 with some hesitation, to the species Ichthyonema gloUceps Kudolphi) on account of the 

 enormous number of young which the adult specimens contain, might, under favorable 

 conditions, become of serious import. I shall speak of it somewhat in detail. The 

 several lots of worms which I refer to this species come from the following hosts : 



1. Bluetish (Pomatomns saltatrix), ovaries, Woods Hole, August, 1884. 



2. Spanish mackerel (Scomberomorus maculatus), ovary, New Jersey coast, S. E. Meek, collector, 



October, 1886. 



3. Black grouper (Lobotes surinamensia), peritoneum, Woods Hole, August 3, 1887. 



4. Black grouper (Lobotes surinamehsis), viscera, Woods Hole, August 6, 1887. 



5. Tarpum (Tarpon atlantlcus), U. S.Nat. Mus. collection, locality and date of capture not given. 



The specimens are all females, and, with the exception of lots 2 and 5, have the 

 uterus, at least its lower portion, filled with embryos. They are all very long and of 

 nearly uniform diameter throughout, and rather bluntly rounded or conical at the 

 extremities. In lot 1 the embryos, which occur in myriads, appear to have escaped 

 by rupture of the uterus into the body cavity. Lot 3 consists of two specimens 

 obtained from the body cavity of their host. They measured living 510 and 580 mm. 

 in length, respectively, and 1.48 mm. in diameter 5 color, brownish. The intestine 

 appeared as a dark-brown line for more than two-thirds of the entire length and as a 

 white line for the remainder of its length. The intestine ends blindly at its posterior 

 extremity. My notes, made at the time of collecting, state that the external opening 

 of the uterus is at a point about 1 mm. from the anterior end, where it was observed 

 that the young were being discharged in vast numbers. Under slight pressure, how- 

 ever, two tubes were seen protruding for a short distance, from each of which young 

 were escaping. This would appear to indicate that the uterus had been broken, and 

 what was taken to be an external opening may have been a break in the body wall. 



The embryos measured about 0.4 mm. in length, 8/< in diameter at the posterior end, 

 and l.'J// in greatest diameter. The anterior end was very slender, appearing as a 

 mere line, even when highly magnified. These embryos are characterized by having 

 a few, about four, dark-brown granular masses scattered along the middle region of the 

 body. A slight notch was noticed at the posterior end of some. A favorite position 

 of these embryos is \\ ith the posterior end bent rather sharply, often so much so as 

 to point forward. The anterior end is also often bent so that the two ends point 

 toward each other. Where they occur in the greatest abundance in the parent worm 

 they impart to the latter a plump and even distended appearance. After the diselia rge 

 of the embryos the worm is transparent, much contracted, quite irregular in outline, 

 and in places flattened and shriveled. I do not know what the history of this worm 

 is between the embryos as seen in these specimens and l lit- adult. The embryos aro 

 eminently well fitted for making their way by means of their attenuated and filiform 

 anterior ends through the tissues of their host, whatever that host may be. If they 

 have a history anything like that of Trichina spiralis, then the animal which would 

 make a meal off of a fish harboring one or more adult Ichthyonema} has trouble ahead. 



While encapsnled nematodes were found in a large number of the species of fish 

 examined, and in considerable abundance in some, they were almost always confined 

 to the body cavity, where they lay in flat coils for the most part on and among the 

 viscera. They were very seldom seen in the flesh. The adults in the alimentary canal 



