analyze these data consecutively from the widest occurrence to the 

 narrowest with the reservation that this wall force us to make a certain 

 repetition of what has been said before. 



The genus Dactylogyrus is discovered on four orders of fishes 

 and Gyrodactylus on ten. We have already said about the first that it is 

 basically characteristic for the Cypriniformes which is parasitized by 213 

 species; whereas the remaining 8 known species are encountered on 7 

 families pertaining to 3 orders. One cannot fail to notice that 208 species 

 are found on one family--Cyprinidae. The second genus is found among 10 

 orders, which are little or not at all related to each other. The fact that 

 more than one -half of the known species were discovered on Cyprinifornnes 

 means nothing, because the degree of information about the genus, and 

 particularly of its distribution on marine fishes is completely insufficient p. 266 

 and its scope beyond doubt is much more significant than what is known to 

 us at the present time. 



Two genera, encountered on fishes of three orders --Microcotyle 

 and Benedenia- -basically, as this was shown earlier, are characteristic 

 for Perciformes. Thus, 75 species of Microcotyle were found on repre- 

 sentatives of this order and only three on the other two. Of the 23 species 

 of Benedenia, 20 were discovered on Perciformes, two on Myliobatidae, 

 and one on Mullet and the last is very doubtful. Beryciformes and Tetro- 

 dontiformes are also hosts for Benedenia, but we do not possess a single 

 independent species of this genus, and both of these orders are closely 

 related to Perciformes. 



Capsala, Calicotyle, Entobdella, are encountered on nnore than 

 three families of two orders of fishes. The first genus is found mostly on 

 Perciformes--l6 species--and also quite normally and in sufficiently great 

 numbers--five species--on Tetrodontifornnes which are relatedta Perci- 

 formes. All seven species of Calicotyle live on Selachiformes and one in 

 addition to that on Plectognathae (holocephalans, nobis) , which, nevertheless, 

 among all the fishes are closest to Selachii and are related to one branch 

 of development- -Chondrichthyes (Nikolski, 1954). It is interesting that 

 this is the only species of monogenetic trematodes encountered on repre- 

 sentatives of different classes (or at any rate subclasses as is supposed by 

 the majority of authors). Entobdella lives basically on Mugiliformes 

 (4 species) and more rarely on Selachii (2 species). 



Axine, Acolpenteron, Dionchus and Hete robothrium are en- 

 countered on three families of two orders of fishes. The first genus 

 parasitizes Beloniformes in a great majority of species (4 species of p. 267 



Axine) and is known from Perciformes (2 species). The consanguinous 

 relations of these two orders are dubious. Acolpenteron is still insuf- 

 ficiently studied but we can consider that it is encountered on clearly 

 unrelated fishes, approximately in the same insignificant number of species 



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