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 Ichthyonema (which I have referred, 
with some hesitation, to the species Ichthyonema glohiceps Rudolphi) 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. Bluelish ( Pomatomus 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 surinamensis), peritoneum, Woods Hole, August 3, 1887. 
4. Black grouper ( Lobotes surinamensis ), viscera, Woods Hole, August 6, 1887. 
5. Tarpum ( Tarpon atlanticus ), 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; 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 13 m 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 with 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 discharge 
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 the adult. The embryos are 
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 Ichthyonemce has trouble ahead. 
While encapsuled 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 
