begin to form in the shape of thread-like pipes and three plates corre- 

 sponding to the terminal part of the supporting apparatus. " The adult 

 wornns (Fig. 158) have edge hooks 0. 015 - 0. 019 mm in length and thus 

 one can consider that no growth is observed among edge hooks of this 

 species, just as among the preceding ones. 



OMtMM 



Fig. 156. Ancyrocephalus (s.lat.) 

 vanbenedeni (Parona and Perugia), 

 attaching armature of the disc of 

 an adult worm from the gills of 

 Mugil auratus Risso from the 

 region of Karadaga (Black Sea). 



Fig. 157. Ancyrocephalus (s.lat.) 

 mogurndae (Yamaguti), attaching 

 armature of a free -swimming 

 larva. (According to Gussew, 1955). 



Ancyrocephalus (s. lat. ) curtus Akme row.- -This worm de- 

 scribed from the Reservoir of Amur from Percottus glehni (Dyb. ) was 

 studied by A. V. Gussew in 1948 - 1949 in Lake Hanka. He hatched nnany 

 larvae and the period of developnnent of their eggs was about 5 days. The 

 length of the larva was about 0. 09 rnm and the width 0. 03 mm. Their 

 structure is typical: they have three zones of ciliary covering; their 

 intestine is circular with a large pharynx. The armature of the attaching 

 disc (Fig. 159) consists of 14 edge hooks--0. 015 to . 017 mm in length 

 and a pair of chitinous thin brackets (embryonic inceptions of the ventral 

 pair of middle hooks) about 0. 016 mm in length. In addition to this, 

 A. V. Gussew once found an immature young worm which still possessed 

 undeveloped dorsal middle hooks and their connecting plate, while having 

 fully fornned ventral hooks and their plate. Adult worms (Fig. 160) have 

 edge hooks 0. 016 - 0. 020 mm in Length, that is they grow somewhat in the 

 postembryonic period. This growth proceeds by way of an increase of 



the round terminal part of the handle which is developed more weakly annong 

 young worms. 



D. 155 



Ancyrocephalus (s. lat. ) pavlovskyi Gussew--In 1948-1949 A. 

 V. Gussew obtained larvae of this species on Lake Hanka. The develop- 

 ment of the eggs continued about 4 days. The larva has three zones of 

 cilia the first- -of eight cells, an equatorial --along the sides of the body 

 of 4 (6?) ciliary cells, and a posterior one (the quantity of the cells has 

 not been determined). The attaching disc (Fig. 161) with 7 pairs of edge 

 hooks 0. 013 - 0.016 mm in length and a pair of powerful sabre - 



shaped inceptions of the ventral middle hooks of about 0, 02 mm in length. 



p. 156 



166 



