(LDlMM 



Fig. 150. Dogielius planus Bychowsky, stages of development of the 

 copulatory organ of the worms from the gills of Schizothorax intermedius 

 McCl. from the River Varzob (Tadjikistan, SSSR). 



4. The developraent of Ancyrocephalus Creplin 



We accept the genus Ancyrocephalus in thebroad sense in the 

 present work. The reason for this appears to be the extremely formal 

 approach of Anierican researchers toward the description of new genera 

 of Ancyrocephalinae and the lack of the opportunity to conduct a special 

 revision of this interesting group at the present time. Undoubtedly, how- 

 ever, considered in such scope this genus is artificial and demands sub- 

 division. It seems to us that from Ancyrocephalus (s. lat. ) one can isolate 

 several independent groups (apparently the actual genera), on one hanu, 

 the group of forms with the type of the genus, Anc. paradoxus Creplin, 

 which have intestinal trunks not merging with each other, and on the other 

 hand, the second group of species with merging intestinal trunks to which 

 are related first of all well-known types; Anc . cruciatus (Wedl. ), Anc. 

 vanbenedeni Parona and Perugia (for more details see the chapter, "A 

 System of Monogenetic Trematodes" pages 348-352), 



The genus Ancyrocephalus (£. lat.) basically resembles 

 Dactylogyrus Diesing in its structure but differs by the presence of four 

 middle hooks on the attaching disc, each pair of which is connected by a 

 special plate. The disc doesn't bear any supplementary chitinous for- 

 mations. Both connecting plates are more or less of a simple form and 

 never articulate with each other. The edge hooks are ordinary and 

 number 14. 



In connection with the above-mentioned understanding of the 

 genus the description of the development is given according to repre- 

 sentative species, because generalized data can subsequently lead to 

 faulty representations concerning the systematics of the group. Certain 

 considerations of general order are expressed at the end of the section. 



162 



