V-shaped, curved chitinous membrane and finally large edge hooks 

 already forming handles" (see Fig. 178). Consequently we see that the 

 development of Bychowskyella takes place in the same fashion as among 

 Ancylodiscoides Yamaguti with the exceptions of differences in the 

 development of the edge hooks. 



8, The development of Heteronchocleidus Bychowsky 



Heteronchocleidus buschkieli Bychowsky (Fig. 118), which 

 was studied by us from aquarium fishes, is a representative of curious 

 tropical monogenetic trematodes, which are related to the family Dactylogyridae 



O.OIhm 



Fig. 179. Heteronchocleidus buschkielli 



Bychowsky, attaching armature of the 

 disc of an adult worm from the gills of 

 little aquarium fish Macropodus opercularis 

 (L, ) Leningrad. 



Fig. 180. Heteroncho- 

 cleidus buschkielli 

 Bychowsky, free- 

 swimming larva. 



(Ancyrocephalinae), parasitizing Anabantldae. The internal 



structure is of the usual type for this family, the presence in the adult 

 stage of three fully developed middle hooks and one (hook, nobis) which 

 is very retarded in development, and many times smaller in size than 

 the rest (Fig. 179) is characteristic for them. The embryonic develop- 

 ment takes place within 5 to 6 days. The free -swimming larva of H. 

 buschkieli (Fig. 180) corresponds to that of representatives of the genus 

 Ancyclodiscoides. Its length is about 0. 07 mm and its width is 0. 02- 

 0.03 mim. The ciliary covering consists of a zone divided into two groups 

 with a weakly developed middle and a larger undivided third. The larva 

 has 14 very tender edge hooks on its disc which are about 0. 009 rnm in 

 length. In addition, somewhat above them, lies the first pair of middle 

 hooks in the shape of slightly curved little parentheses of slightly greater 

 length than the lateral hooks (0. 009 - 0. Oil mm) (they are not expressed 

 on the drawing because of their unusual frailty). The connecting plate of 

 the first pair and the second pair of middle hooks are still absent. The 



p. 165 



177 



