456 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



ternal parasites were collected mainly by Dr. Edward Palmer, and will 

 be of great interest when carefully studied and described. As yet, noth- 

 ing more than a casual examination of them has been made. These 

 internal parasites were found in nearly all kinds of fishes, chiefly in the 

 stomach and intestines, but also very frequently in the flesh, or among 

 the abdominal viscera, or in the air-bladder, or even in the eyes, &c. 

 The internal x>arasites were mostly worms, but these belong to four very 

 distinct orders. 



1st. The " round-worms," Nematodes. 



These are related to the round- worms so frequent in the intestines of 

 children, and also to the notorious Trichina of man and the hog. One 

 or more species are found in the intestine and stomach of nearly every 

 kind of fish, and frequently, also, in the liver, peritoneum, eyes, and 

 various other organs. One species, two or three inches long, is very fre- 

 quently found coiled up spirally in the flesh of the cod. Another large 

 species is frequently found in the flesh of the tom-cod, or frost-fish. 

 Although these are not dangerous to man, they are very disagreeable 

 when found in fish intended for food. 



A species belonging to this group is very frequently found in the body- 

 cavity of one of our species of Sagitta (see page 440). 



2d. The flat- worms or " flukes," Trematodes. 



These are short, more or less broad, depressed worms, which are pro- 

 vided with one, two, or more suckers, for adhering firmly to the mem- 

 branes. They pass through very remarkable transformations, as do 

 most of the other parasitic worms. Species belonging to this group are 

 common in the stomach, oesophagus, and intestine, and also encysted or 

 in follicles in the mouth, liver, peritoneum, and various other parts of 

 the body. 



3d. The thorn-headed worms, Aeanthocejphala. 



These have an elongated roundish body, with a proboscis at the an- 

 terior end, covered with hooks, or recurved spines. The proboscis and 

 front end of the body can be withdrawn and thrust out at pleasure. 

 Such worms are very common in the stomachs and intestines of fishes, 

 and are, perhaps, the worst parasites that torment them. The young of 

 these worms also occur quite frequently, encysted in the liver, peri- 

 toneum, throat, mouth, and other organs. 



4th. The " tape- worms," or Cestodes. 



These are long flat worms, divided into many distinct segments, and 

 are very frequently found in the intestines of most fishes. There are 

 numerous species of them, ranging in size from less than an inch to 

 many feet in length. 



Although parasitic worms are found in nearly all kinds of fishes, they 

 are most frequent and in the greatest variety in the large and very vor- 

 acious kinds, such as sharks, rays, the angler or goose-fish, salmon, blue 

 fish, cod, haddock, &c. 



Nor are other marine animals free from these internal parasites. Cer- 



