Many species are encountered on the surface of the body, among 

 these are Microbothriidae , many Monocotylidae and Capsalidae, Acantho- 

 cotylidae and a number of Gyrodactylidae . The latter settle mainly on the p. 75 

 surfaces of the head, whereas Acanthocotylidae settle on the ventral and 

 dorsal surfaces of the body. Monocotylidae and Capsalidae settle on either 

 side, more or less indifferently, whereas Microbothriidae settle, apparently 

 preferably, on the dorsal sides of the body of their hosts. 



Many lower Monogenoidea, mainly Gyrodactylidae and more 

 rarely Dactylogyridae live on the fins. In addition, Calceostomatidae cer- 

 tain Microbothriidae and also, where found, Monocotylidae and Capsalidae 

 usually act as parasites on the fins. The species which act as parasites of 

 the fins occur nnore often on the pectoral, than the dorsal, and more rarely 

 on the caudal, ventral, and anal fins. Calicotylinae inhabit the rectal cavity 

 and its vicinity among shark-type and holocephalan fishes. Until the pre- 

 sent time only three species of Acolpenteron parasites of Cobitidae, Cato- 

 stomidae and Centrarchidae were discovered in ureters. 



The special monogenetic genus Dictyocotyle (D. coeliaca Nybelin) 

 parasitizes the body cavity of certain types of skates. 



Until the present time the only type found in the bood system is 

 Amphibdella torpedinis Chatin. Ruszkowski (Ruszkowski, 1931), studying 

 Torpedo ocellata Ruszkowski and T. nnarmorata Risso at the Naples Zoolo- 

 gical Station, found adult worms in eight specimens of the first species (or about 

 35 per cent of those examined) and eggs in twelve individuals (or about 50 

 per cent); among T. marmorata only eggs were discovered in the heart. In 

 this connection numerous worms were found in the normal habitat, that is 

 the gills. Ruszkowski supposes that either the larvae which emerge from 

 the eggs .penetrate into the blood system and there reach maturity and then 

 lay their eggs while the newly acquired larvae perish or the adult worms 

 penetrate the blood stream (with the help of the head glands?) and there 

 remain without changing morphologically, but adapting themselves to the 

 new conditions. Indisputably, one must consider such location aberrant. 



The parasites of amphibians and reptiles, i.e., representatives 

 of Polystomatidae and Sphyranuridae, settle on the skin, gills, buccal cavity, 

 under the eyelids and in the urinary bladder. The only species indicated for 

 mammals, Oculatrenia hippopotami ,Stunkard, was described from the eye of a 

 hippopotamus (see page 219 ). The parasite of cephalopod moUusks-- 

 Isancistrum loliginis Beaughamp lives in the gills of Loligo media Linne'T 



Representatives of Diclidophoridae are encountered on parasitic 

 Isopoda (for instance Choricotyle charcoti (Dollfus) on Meinertia oestroides 

 or Choricotyle snnaris Ijima on the caudal segment of Cymothoa sp. sp. ); 

 however, we are not inclined to consider these cases as specifically para- 

 sitic action because the same types of Diclidophoridaeare encountered on 

 the gills of fishes which are the hosts of these Isopoda. 



72 



