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 comical proboscis aud termi- 

 nal os like that of Eeheneibotlirium. 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 mm . When placed in fresh water they are apt to assume a filiform 

 shape, with a length of from 4 to 6 mm . When disturbed they contract 

 to 1.5 uim or less. Many of these larvae 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. Larva? 

 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. 8 and 9.) 



Elongated cysts were found in the liver, or peritoneum, of most of 

 the Teleostei 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 Cercarkc in a Sporocyst. 



In other cases the neck of the embryo is protruded from the side of 

 the blastocyst in the form of a loop. 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 Tcenia. 



Nematods were found in most of the fish that were examined, both 

 free in the alimentary canal and encapsuled in the peritoneum, gastric 

 caeca, 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, Agamoncma capsular ia 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, Wematoidea, or 

 Acanthocepliala. These will be described in a subsequent paper. 



The only fishes that were found comparatively free from intestinal 

 parasites were the Sea-Bobins (Prionotus), while a Sturgeon (Acipenser 

 sturio) yielded but one specimen, a Nematod from the alimentary canal, 

 and a few Trematods from the gills. 



