Plectanocotyle on the other. For both the appearance of newly formed 

 clamps, which are similar in structure, as well as the characteristic 4 pairs 

 of the remaining families of Anthocotylinea is characteristic (Dogiel, 1954a). 

 They are the two youngest families of the present suborder, not counting 

 Protomicrocotylidae which most probably separated from Microcotylidae, p. 459 

 although it is not possible to speak about this with certainty (see page 444 ). 



Thus, on the basis of what has been said before we can visualize 

 the general nature of the correlations of Monogenoidea in the form of the 

 appended general diagrami (Fig. 310). This diagram does not pertain to a 

 great degree of accuracy, nevertheless it reflects the interrelations of 

 separate groups and of time in a certain measure. The latter can undoubtedly 

 arouse great doubts and possibly be subjected to very severe criticism. 

 Nevertheless, it is impossible to visualize from contemporary distribution 

 on the hosts (and in separate, more fully studied cases, also the geo- 

 graphical) that the present determination of the historical links between 

 separate groups of parasites could be fornned in a different determination 

 of time of the separation of the separate groups, [i, e_. it is impossible 

 to visualize from their present distribution on the hosts (as well as their 

 geographical distribution) that the nature of the historical links between the 

 separate groups of parasites could be any other way; or, in other words, 

 using these techniques and these data the present solution seems the only one 

 possible, nobis] . This determination of time is obviously very relative 

 and allows errors of many hundreds of thousands of years; however, it 

 gives a general idea about the nature of the tempo cf the evaluation of the 

 large systematic categories of Monogenoidea. 1 



1 



Supplement to proofreading. V. B. Dubinin drew my attention to the 

 book of Baer, (J. G. Baer, Ecology of Animal Parasites, University of 

 Illinois Press, Urbanna, 1952), in which the evolution of the attaching disc 

 of the monogenetic trematodes is represented in the form of a diagram on 

 page 118. As is clear from the preceding text this diagram does not 

 correspond at all to reality and does not have any evolutiophylogenetic, nor 

 relative nor comparative anatomical significance. It is interesting because 

 it illustrates to what errors the sole examination of morphological studies 

 alone can lead. Thus all the variety of forms of the attaching apparatus of 

 Monogenoidea are derived from the disc of Udonella , i. e. , a group which 

 does not have a direct connection with monogenetic trematodes (see A. V. 

 Ivanov, 1953). Furthermore, the disc of Benedenia gives origin to the one 

 of Gyrodactylus, the disc of Tristoma to Heterobothrium etc. In 

 addition to that, a line is extended from Heterobothrium to Polystonna and 

 from the latter to Sphyranura. Thus, Baer does not even see the principal 

 difference between the complex chitinous apparatus of the clamps of 

 Heterobothrium and the suckers of Polvstomatidae. Further comments 

 seem unnecessary to us. 



551 



