greatest width is at the level of the first or second pair of eyes); the 

 attaching disc is almost rovuid, about 0. 025 — 0. 028 mm across; the 

 dimensions of the pharynx are about 0. 01 - 0. 008 mm. The attaching 

 armature consists of 14 edge hooks 0. 008 - 0. Oil mm in length. The 

 ciliary epithelium of the larva is cast off at different times. One can 

 often observe the settled larvae with a part of the ciliary cells which 

 have been retained. The latter fall off in groups, at first on the attaching 

 disc and the anterior end of the body. The cone-shaped growth, on which 

 the third zone of cilia is located, falls off as a unit as is evident from 

 Figure 184. 



001mm, 



Fig. 184. Lamellodiscus 

 fraternus Bychowsky, free- 

 swimming larva casting off the 

 cone of the ciliary zone of the 

 posterior end. 



:j 



H^ 



«/;/«« 



O.OlHH 



Fig. 185. Lamellodiscus elegans 

 Bychowsky, attaching armature of the 

 disc of the larva in the process of 

 development from the gills of Sargus 

 annularis (L. ) from the region of 

 Karadaga (Black Sea). Explanation in 

 text. 



p. 168 



Strange as it may seem the larvae which have just settled are 

 somewhat snnaller in size in comparison with the free -swimming stage. 

 Thus, the youngest larvae which are discovered on the gills of the host, 

 have the length of 0. 06 - 0. 07 mm and a width of 0. 025 - 0. 035 mm. They 

 begin to feed very quickly and their attaching disc acquires the trans- 

 versly elongated shape characteristic for the genus. The edge hooks 

 stop growing completely and retain their initial sizes during the entire 

 life of the worms. The middle hooks begin to form alnnost simultaneously 

 and grow quickly. At first they have the shape of weakly curved plates of 

 the same width for their entire length with a sharply bent and sharpened 

 lower end--the point of the hook (Fig. 185, A). Somewhat after the in- 

 ception of the middle hooks the central connecting piece appears in the 

 form of a straight or slightly curved and hardly noticeable little plate 

 (Fig. 185, B). 



181 



