In cases of finding monogenetic trematodes on more distant 

 genera of the hosts, it appears during their verification that this is either 

 a result of some mistake in the determination of the host or the parasite, 

 or the species of the parasite is represented by certain lowest taxonomic 

 units (subspp. ?, nobis ), the occurrence of which is characteristic only for 

 a certain genus of hosts but not for all, which is analogous to what we saw 

 earlier in Gyrodactylus arcuatus (page 223 ). 



We shall summarize certain results without stopping to analyze 

 the species encountered on representatives of a single genus be- 

 cause there are no doubts whatsoever that these species of hosts basically 

 are phylogenetically very close to each other. ^ 



1 



In the work which was cited by us in 1933 we examined a special case 

 where the degree of parentage of the hosts related to one genus of Abramis 

 arouses certain doubts. To summarize, the analysis of the occurrence of 

 the species of Dactylogyrus peculiar to the separate species of fishes shows 

 that it is possible that the species of the genus Abramis should be placed in 

 three different genera. During subsequent works, however, new data were 

 received about the occurrence of D. auriculatus Nordm. on_A, ballerus 

 which indicated that the Cinets (A. ballerus, nobis) is possibly closer to 

 the Shch (A. sp. nobis ) than the Beloglazka (A. sepa , nobis ). 



As the preceding analysis has shown more or less accurately, only 

 32 species or 3. 3% of the total number of the previously examined mono- 

 genetic trematodes are encountered on fishes of different families of one 

 or several orders. However, during the verification of the occurrence of 

 these species we succeeded in showing that the great majority of them is 

 found on fishes which. have to a certain degree, consanguine links with 

 each other, and in this fashion do not represent special exceptions to the 

 general rule about the occurrence of the species of monogenetic trematodes 

 on consanguinous fishes--a rule which undoubtedly emerged (is the logical 

 outcome, nobis) from everything that has gone before. Only nine species 

 do not fit into this rule of which (Calicotyle affinis S cott and Gyrodactylus 

 arcuatus Bychowsky) are encountered on fishes of two different, unrelated 

 orders and seven [ Ancyrocephalus manilensis Tubangui, A. mogurndae 

 (Yamaguti), Trochopus tubiporus (Diesing), Heterocotyle minima (Mac- 

 Callum), Squalonchocotyle abbreviata (Olsson), Pseudaxine indicana 

 Chauhan and, Microcotyle pomacanthi MacCallum] occur on several 

 families of one order of fishes which are only slightly related. If we 

 should examine once more the data on the finding of these nine species, we 

 could express certain supplementary doubts about the correctness of 

 placing six of these species in the given group. Thus, even though it is 

 encountered on fishes of different orders, G. arcuatus forms special sub- 

 species which are characteristic only for the fishes of the determined 



272 



