N. stoliczkai, and ? N. sewerzowi. N. sewerzowi occupies a more or 

 less undetermined place in this list. It has a high percentage but low 

 intensity of infection, and it is for this reason that it is indicated with a 

 question mark in two places. If we turn to the ichthyological data, 

 we shall see thatj^. dorsalis , N . strauchi and N. labiatus belong to the 

 subgenus Deuterophysae, the remaining two species to the subgenus 

 Kemachilus (s. str. ). Within the linnits of the first subgenus, _N. dorsalis 

 and N. strauchi are closer to each other and the latter in its turn is close 

 to NT~labiatus. The following data serves as a basis for this. N. strauchi and 

 N. dorsalis apparently form hybrids among themselves; in any case a 

 subspecies N. strauchi dorsaloides intermediary between^, strauchi 

 ulacholicus and N. dorsalis is described from the region of Issik-Kulya 

 (Turdakov, 1947). On the other hand ^wo variations which apparently 

 represent hybrids of this species with N^ strauchi are known for J^ labiatus 

 (Berg, 1949, page 857). Thus, according to the degree of consanguinity 

 the examined fishes can be arranged as follows: _N: dorsalis - -N . strauchi -- 

 N. labiatus --N. stoliczkai, which as we see fully corresponds to the list 

 composed in accordance with the nature of infection by G_. nemachili . The 

 question about the status of N. swerzowi remains unclear. Obviously, it must 

 be solved by ichthyologists, but taking into consideration the data on G. 

 nemachili and the fact that the swim bladder of this fish has a free part 

 and also that it is small and resembles the one among representatives of 

 the subgenus Deuterophysa (see Berg, 1949, page 851), it seems probable 

 to us that this species is placed erroneously in the subgenus Nemachilus 

 8. str. and that it stands closer to Deuterophysa . If this is substantiated 

 then its high percentage of infection and at the same time its low degree 

 of intensity will become fully understandable. All in all, we notice almost 

 complete coincidence of the data on phylogenetic relations of fishes with 

 the character of infection of the "basic" and "secondary" hosts. 



As a result of the examination of the entire material on 

 occurrence of species of monogenetic trematodes on the species and 

 genera of fishes, one can consider as fully established the following: 



1. A great majority of species of nrionogenetic trematodes is 

 encountered only on one species or representatives of one genus of fishes. p. 248 



2. When mionogenetic trematodes are encountered in several 

 genera of fishes, the latter stand in phylogenetic relations and, in an overwhelming 

 majority of the cases>are related to one family. 



3. The finding of species of monogenetic trematodes on the 

 representatives of different families of one or several orders of fishes 

 occurs rarely and in these cases one can show that consanguinous links 

 exist between the hosts. 



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