one observes a certain delay in the inception of subsequent elements along 

 with a larger size of hooks. Thus, middle hooks of the first pair reach 



RDIhh 



aoifM 



Fig. 173. Ancylodiscoides sp. sp., attaching armature of a developing 

 larvae from the gills of Silurus glanis L. frona the Delta of the Volga. 

 Explanation in the text. 



considerable size (Fig. 173, C), where- 

 as the inceptions of their connecting 

 plate is not yet observed. Later, even though the 

 first pair of middle hooks and their plate 

 are fully formed the inception of the 

 second pair will still not be observed 

 for a long time (Fig. 173, D). 



After the inception of the second 

 pair of middle hooks the larva grows 

 rather slowly. During that time the 

 larva (Fig. 174) has a length of about 

 0. 23 mm and a width of 0.08 mm (in a 

 somewhat compressed condition). The 

 edge hooks are of final shapes and sizes 

 (0.015 - 0.017 mm, i.e., they have grown 

 scarcely noticeably) --the first pair of 

 the middle hooks is of the customary 

 shape for the adult worm; its sizes: 

 length 0. 024 mm, the basal part 0. 022 mm, the 

 interior offshoot 0. 009 mm, the exterior 

 0. 003 mm and the edge or point U. Ui3 mm. 

 The connecting plate is fully developed, 

 its length is 0. 040 mm. Above the 

 attaching disc lie two middle hooks in 

 the shape of parallel parentheses which 

 are curved at the upper end and 



Fig. 174. Ancylodiscoides 

 siluri Zandt, the larvae with the 

 recently formed second 

 pair of middle hooks on 

 the atUching disc from the 

 gills of Siluris glanis L. from the 

 Delta of the Volga. 



174 



