Dr. Kassai Tibor szerk.: Parasitologia Hungarica 2. (Budapest, 1969)

appearing mainly on fish inhabiting the draining channels of fish ponds; in these sites it is not uncommon, occurring principally on the crucian carp, the common sunfish, and the bitterling, with a 50 per cent infection of the imaginai forms. There was a 100 per cent occurrence of copepodite forms in certain fish groups; the parasites are frequently to be found, not only on the body surface, but also on the gills and even in the nasal cavity

. An infection, considered serious so far as our natural waters are concerned, was observed on a young pike from the River Ipoly. With regard to Lake Balaton, Tracheliastes maculatus deserves special attention; according to GEYER'

s (1939 c) observations, it can be found on 50 per cent of the bream population. On this parasite, and even more on its near relation, Tracheliastes po ly colpus

, the occurrence of certain Epistylis species is almost without exception. (Those found on Tracheliastes maculatus have been identified as Epistylis nympharum by GEYER). These unicellular commensals occasionally cover the crustaceans to such a degree that the latter can be recognized only by close scruting. The distribution of Ergasilus nanus in Hungary is limited to fish inhabiting the rapid cold mountain streams: So it can be regarded as rather rare in Hungary

. The occurrence in Hungary of Paraergasilus rylovi was first mentioned by JACZÓ (1961) who found this crustacean on Abramis brama, Carassius carassius, Rutilus rutilus, Cyprinus carpio, and Amiurus nebulosus in the tributaries of the River Tisza at Szajol. Our own investigations have shown it to be equally present in the Rivers Tisza and Danube. Despite its apparent frequency it has been recorded only rarely, probably because only relatively recently have nasal cavities been examined during routine investigations.