PART III 



SYSTEMATICS AND PHYLOGENY OF 

 MONOGENETIC TREMATODES 



CHAPTER 1 



BASIC DIRECTIONS OF PHYLOGENY OF 

 MONOGENETIC TREMATODES 



In considerations of the phylogeny of monogenetic trematodes we p. 323 



must first of all bear in mind that all our constructions are based only 

 on indirect data, for paleontological remnants of these worms are un- 

 known. In order to reconstruct the phylogeny we must utilize the in- 

 formation of the data of comparative anatomy, on the postembryonal 

 development of worms and finally, as we attempted to show earlier, 

 the data on their occurrence, In addition, the latter can to a certain 

 measure, if not replace them, at any rate, reflect paleontological 

 materials, because even though it is not quite complete neverthe- 



less considerable information on paleontology of the hosts exists. One 

 caruiot fail to note that we can apply also our data on life cycles to the 

 construction of phylogenetic schemes because the nature of the latter 



shows that the existence of parasites and hosts which finds its reflection 

 in the complexity and "tight-fitness" (closely coordinated character, 

 nobis) of their life cycles, bear a very ancient nature in a number of 

 cases. 



We suppose that the presence of materials on all the sections 

 which we have indicated allows us, in the re-creation of the history of 

 the development of the group as a whole, to consider that the schemes 

 obtained by us reflect accurately the process which took place in actuality. 

 Completely understandable and possible errors will pertain mainly to 

 individual details and not to the general direction and basic lines of 

 development. 



Although D. M. Fedotov (1938) objected to our schennes 

 published in the work of 1937, considering as inadmissible the repre- 

 sentations of the schemes in time without the presence of paleonto- 

 logical material on the given group, we completely disagree with him. 

 The data on the paleontology of the hosts plus the analysis of the relations 

 of the latter with the parasites living on them allow us to tie the stages 

 of development of monogenetic trematodes to specific historical periods 

 with a sufficient degree of probability. In our research we widely employ 

 the generalizations of V. A. Dogiel about oligomerization and poly- 



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