512 KEPORT OF COMMISSIONER OF FISH AND FISHERIES. 



every fish of the genus Cyprinus; it is called tbe Caryophyllaeus mutabilis. 

 It lias only one joint, closely connected with the head, which develops in 

 the same fish, and forms the connecting link with a long and varied 

 series of maritime forms, which in their youth live in osseous fish, and 

 with these migrate into rays and sharks, where they reach maturity. 

 These are the Tetraphyllidw of Van Beneden, which have four sucking 

 disks which are either unarmed or have hooks or stings. To the former 

 belong the UcMnobothrium, Fhyllobothrium and Anthohothriumj to the 

 latter, the Acanthohothrium, Calliohothrivm, and Oncliobothrium. The 

 Uchmobothrium found in the ray has only two sucking disks, but two 

 sharp stings on the forehead, and a neck full of long bristles. J^ext to 

 this comes the Tetrarhyncus, which has four hooked trunks. When 

 quite young it is found in plaice, and when fully grown in rays and 

 sharks. Xearly related to this one is the Trimnophorus nodulocus with 

 two pairs of three-pronged hooks, which in its undeveloped condition is 

 found in the liver of fish of the genus Cyprinus, and when fully ma- 

 tured in the intestinal tube of fish-of-prey. 



The Cestodes found in fresh- water fish are not so numerous and varied 

 as those of the salt-water fish. Of the latter there may still be men- 

 tioned the Bothriocephalus punctatus of the plaice, and the Bothrioceph- 

 alus rugosus of the codfish ; and of the former, the Bothriocephalus pro- 

 boscideiis of the salmon, the Taenia oceUata of the perch, the Toenla 

 osculata of the "Wels," Silurtis glanis, and the Tccnia t&rulosa of the 

 "Orf," the Tcvnia longicoUis of the salmonoids, mostly confined in cap- 

 sules, and the Tcenia macrocephala of the eel. 



The Trematodes may be subdivided into a number of families accord- 

 ing to the number and position of their sucking disks. In this way we 

 may distinguish the Monostoma, Bistoma, Tristoma, Poly stoma, Holostom a ^ 

 and Amphistoma. The sucking disks of the lower extremity are some- 

 times furnished with hooks as, for example, in the Gyrodactylus. 



The last of this kind is the Biporpa, which in the middle grows 

 together with another individual, and then forms a peculiar twin-animal, 

 the Diplozoon paradoxum. The monostoma are rarely found in fish. 

 They are found in the intestinal tube of the stickle-back {M. carryophyl- 

 liniim), and the barbel {M. cochlear iforme), in the gills of the "brachse"' 

 (ilf. praemorsum), and in capsules in the smaU "Marana" {M. Maraenulce). 

 Von Nordmann found an incredible quantity of a youthful formation 

 {Diplostomum) of the Holostoma living in aquatic birds, in the eye of the 

 perch, the burbot, fish of the genus Gyprinus, and in the last mentioned 

 also in the skin. In the lens of the eye of the burbot, 290 such little 

 animals were counted, whilst the vitreous humor contained about half 

 that number. This must of course make the fish more or less blind. 



The Bistoma are very common in fish. Thus the perch has five dif- 

 ferent kinds, and the eel ten. In our fish the most frequent are the 

 Bistomum globipornm, the B. tereticoUe of the burbot, -pUie, salmon, and 

 trout, the D. nodulosum of the perch, the B. torulosnm of the " VVels,'' 



