It is not possible to doubt that all these five families des- 

 cend from groups and forms which parasitized the Perciformes also 

 and thus they are all closely connected with the latter from the be- 

 ginning of their evolution. The five families which are encountered 

 on Perciformes and on one more family (order?, nobis) are apparently 

 phylogenetically also primary parasites of Perciformes. Thus, Calceo- 

 stomatidae, even though they are encountered also on Cypriniformes, 

 their basic genera--Calceostoma and Calceostomella, beyond any 

 doubt are purely marine in origin and are encountered only on Perci- 

 formes. We have already spoken about Dionchidae discovered also on 

 Echineiformes (see page 228 and 256). Anthocotylidae, encountered 

 also on Gadiformes, have primary genera parasitizing Perciformes^ 

 which is shown later (see page 426). With only one exception (see 

 page 274 ) Gastrocotylidae parasitize Perciformes. The exception of 

 this group is formed by Mazocraeidae, which apparently are secondary 

 parasites for Perciformes which transferred to these fishes from 

 Clupeiformes (see pages 307 and 417 ). As regards the families of 

 Monogenoidea encountered on several orders of fishes, taking into 

 consideration what has been said in the chapters about occurrence of 

 the families and about the system of Monogenoidea, we can say that in 

 contrast to Gyrodactylidae and Dactylogyridae; Capsalidae, Diclido- 

 phoridae, Diplectanidae, and Microcotylidae are phylogenetically 

 primary parasites of Perciformes. As regards Acanthocotylidae they 

 are apparently ascribed here erroneously (see page 275 ). Within the 

 limits of Dactylogyridae the relations are apparently complex. Thus 

 Dactylogyrinae, of which only few representatives of the genera 

 Dactylogyrus and Acolpenteron are encountered on Perciformes, are 

 undoubtedly secondary for the present fishes and transfer to them 

 from Cypriniformes. In contrast to this Ancyrocephalinae are in- 

 digenous parasites of Perciformes, and transferred onto other orders 

 from them, as was partially shown earlier. It is characteristic that 

 for the total number of 26 genera, 18 are encountered on Perciformes 

 and in the analysis of independent genera encountered only on other 

 orders it is clearly apparent that the majority of them originates from 

 widely distributed genera of Ancyrocephalinae of Percifornnes. An 

 exception is fornned by the closely related genera Ancylodiscoides, 

 Hamatopeduncularia, and Bychowskyella which apparently are of very 

 ancient origin and sharply stand out among the rest of Ancyrocephalinae 

 (see page 351 ). We shall return later (see page 346 and further) to the 

 correlations of the groups within the limits of Dactylogyridae. P- 315 



Gyrodactylidae, which are distributed very widely in which 

 they are helped by their very great mobility and the means of infection 

 of the hosts by adult individuals (see page 131 ), are very poorly studied. 

 Nevertheless, we are inclined to think that their phylogenetic roots are 



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