CONCLUSION 



Let us draw certain conclusions. The problems of our research p. 47 

 were the working out of a system, and the establishment of the basic trends 

 of evolutionary process of monogenetic trematodes. The reconstruction of 

 these -ways in the absence of paleontological data is a very complex business, 

 but unfortunately for the vast majority of groups of invertebrate animals one 

 has to deal without them. The utilization of all available material which, 

 through accumulation and superposition for comparisons and mutual cor- 

 rection, allows us to make more or less convincing conclusions is that much 

 more important. It seemed to us that comparative anatomical data, data 

 on the biology of adult animals, materials on postembryonic development, 

 basic moments of the life cycle, occurrence of monogenetic trematodes 

 on their hosts, indicating here also the information about the nature of fauna 

 of Monogenoidea on determined large groupings of their hosts, and finally 

 information about the phylogeny of their hosts, which is based on their 

 paleontological remains, can serve as such material for the class under 

 study for the purposes and aims that interest us. 



During the analysis of the comparative anatomical data, we de- 

 parted from two basic ideas which seem to us very fruitful for the attempts 

 of the study of the phylogeny of any group. The first of them is the thought 

 about the presence in each group of determined evolutionary 

 tendencies, determined by morphological peculiarities of the group, which 

 is developed in the changing conditions of the external medium in relation to the 

 animal, and surrounding them. These evolutionary tendencies 



are reflected in the structure, not only of separate organs of their systems, 

 but primarily of the entire organism as a whole. To show the presence of 

 these tendencies within the limits of a particular group is a very rewarding 

 problem and it seems to us that we succeeded in some measure in solving it 

 in connection with the monogenetic trematodes. 



The second idea w^hich helped us in the comparative anatomical 

 research of Monogenoidea from the point of view of the phylogenetecist is 

 the theory of oligomerization of V. A. Dogiel. Its role is fully understandable. 

 However, note that in our materials is indicated one more important principle 

 about which we write in our review of the book of V. A. Dogiel (Bychowsky, 

 1955). This principle could be called the principle of the change of pro- 

 cesses of oligomerization by the processes of polymerization. This 

 principle, noted but not developed by V. A. Dogiel, allows us to understand 

 a number of important neculiarities of the development of different groups 

 of animals and also gives into the hands of the researcher materials for analysis of 

 the reasons for the changes in the evolutionary direction of groups under examination. 

 V, A. Dogiel was sympathetic to the consideration ex- 

 pressed by us on this subject and we hope that in the process of further p. 479 

 working out of the theory of oligomerization he will dedicate special study 

 to these questions. 



573 



