454 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [2] 
The apex of the head, at times obtuse or even retuse, is frequently ele- 
vated into a terminal papilla, disclosing a conical proboscis and termi- 
nal os like that of Hcheneibothrium. The entire head is sometimes invagi- 
nated. The length is difficult to determine, on account of the extreme 
variability of form, but the average length when at rest is not far from 
2.5™™, When placed in fresh water they are apt to assume a filiform 
shape, with a length of from 4 to6™". When disturbed they contract 
to 1.5™™ or less. Many of these larvee have two small red blotches im- 
mediately behind the bothria. A water vascular system can be distin- 
guished in most of them. This consists of a convoluted tube on each 
margin, becoming evidently double near the head and forming a loop 
in front of the bothria and giving off branches to the bothria. Larvze 
resembling those from the gall-bladder, but smaller, were also found in 
the intestine of the Squeteague (Cynoscion regale) and of the Angler 
(Lophius piscatorius). These, wherever noticed, were in myriads, float- 
ing free in the chyle. (Plate VI, Figs. 5 and 9.) 
Elongated cysts were found in the liver, or peritoneum, of most of 
the Teleostet that were examined. These when opened set free an en- 
docyst which is contractile and has the power of locomotion to some 
extent. When subjected to the action of the compressor, lateral ves- 
sels can be discerned which are evidently parts of a water vascular 
system. When one of these endocysts (blastocysts Diesing), that is suffi- 
ciently developed, is opened, it will be found that an embryo has been 
developed within. In some, this embryo seems to be free in the paren- 
chyma, and when the wall of the blastocyst is ruptured, it is at once 
freed from its living envelope. The development in this case seems to 
be analogous to the development of Cercarice in a Sporocyst. 
In other cases the neck of. the embryo is protruded from the side of 
the blastocyst in the form of aloop. When further pressure is applied 
the head is released, while the blastocyst remains attached to the scolex 
much like the bladder of a Cystocercus. The embryo, however, it will 
be observed, is not released by evagination, as in Tenia. 5 
Nematods were found in most of the fish that were examined, both 
free in the alimentary canal and encapsuled in the peritoneum, gastric 
ceca, liver, &c. They were found in the greatest numbers in the peri- 
toneum of the Angler (Lophius piscatorius), from a single specimen of 
which hundreds of the Nematoid, Agamonema capsularia Dies., were 
obtained. . 
Several Trematods were met with, most of them free in the stomach 
of their host, but not so abundant as either the Cestoidea, Nematoidea, or 
Acanthocephala. These will be deseribed in a subsequent paper. 
The only fishes that were found comparatively free from intestinal 
parasites were the Sea-Robins (Prionotus), while a Sturgeon (Acipenser 
sturio) yielded but one specimen, a Nematod from the alimentary canal, 
and a few Trematods from the gills. 
