attaching disc but forms a small break on the very posterior end on which 



a small, hill-shaped growth is located. Altogether the ciliary covering of 



the larva carries evident traits of bifurcation into right and left independent 



halves. The casting off of the ciliary epithelium takes place unequally: the p. 181 



middle zone is shed last. The attaching armature (Fig. 201) of the larva 



consists of 14 edge hooks and 3 pairs of middle hooks. The edge hooks 



are 0. 012 - 0. 015 mm in length. They are of the usual dactylogyrid-form 



with a handle of constant thickness 



in its entire length. The sizes of 



the edge hooks do not change during 



the entire life of the worms. The 



first pair of middle hooks lies near 



d.lMM 



(LOlMfi 



Fig. 201. Benedenia derzhavini 

 (Lajman), attaching armature of 

 a free -swimming larva. 



Fig. 202. Benedenia derzhavini 



(Lajman), middle hooks of an adult 

 worm from the gill cavity of 

 Sebastodes schlegeli (Hilg. ) near 

 Vladivostok (Sea of Japan). 



the posterior end of the attaching disc. They have the shape of the middle 

 hooks of Dactylogyridae with undeveloped offshoots resembling the hooks 

 of Nitzschia but relatively more massive. The length of this pair in D. 

 derzhavini is about 0.028 - 0.03 mm. The second pair of middle hooks 

 lie sonnewhat closer to the center of the attaching disc, leaning with the 

 lower half against the first. The hooks of this pair resemble the middle 

 hooks of the lowest groups with a basal part which is long but compressed 

 at the sides and rounded on its free end and changing on the opposing end 

 into a small, sharply-curved point. Along with this, a small sharpened 

 offshoot, as if it were a small second point, departs at the place of its 

 determined beginning along the exterior curvature of the hook in the 

 opposite direction. The length of the hook of the third pair is about 0. 038 

 0. 04 nnm. The third pair of middle hooks lies almost at the center of the 

 attaching disc and has the shape of little sticks bifurcated at the lower end 



196 



