massive than the other. Both hooks resemble the developing hooks of the 

 dactylogyrid-type with a fully developed basal part and undeveloped ex- 

 tensions. In one of them the upper edge is truncated, almost straight and 

 somewhat thinned in the middle, whereas the anterior edge is considerably 

 thickened. The second hook gives the impression of being somewhat nnore 

 developed, in it two extensions are noticeable, so to speak. The Znd pair 

 of hooks also is not altogether similar to those of M. spinicirrus, the 

 middle hooks lie on the posterior end of the disc and the first pair is closer 

 to its longitudinal axis. The sizes of the middle hooks of this larva are 

 0. 016 mm, and the 1st pair of the middle hooks --0. 045 mm, and the 2nd-- 

 0.051 mm. The subsequent stages of development resemble the free- 

 swimming larva of M. mugilis Vogt. Its average length is about 0. 35 mm 

 with a width of 0. 1 mm. The larva has an elongated form (Fig. 250) with 

 a well-developed attaching disc located in such a way that the ends of its 

 middle part strongly extend beyond the general contour of the body and 

 contain in them more-or-less developed clamps, on. on each side. These 



Fig, 250. Microcotyle 



gotoi Yamaguti, larva 

 with one pair of clartips 

 and one offshoot from the 

 gills of Hexagrammos 

 octogrammus (Pal. ) 

 from the region of 

 Yablichnoii (southern 

 Sakhalin, Sea of Japan). 



Fig. 251. Microcotyle gotoi Yamaguti, 

 part of the attaching disc of the larva with 

 one pair of clamps and one posterior off- 

 shoot fronn the gills of Hexagrammos 

 octogrammus (Pal.) from the region of 

 Yablichnoii (southern Sakhalin, Sea of 

 Japan). 



lateral growths lie in a different plane (closer to the back) than the re- 

 maining part of the disc. The disc extends beyond the growths in the 

 shape of a rather long very mobile offshoot and in normal conditions is 

 almost rectangular or square shaped (about 0. 06 x 0. 05 mm). Just as 

 in all the subsequent stages of developnnent the larva does not have a 

 pigmented eye. Three groups of efferent ducts of the head glands open 

 at the anterior end. There are two well-developed suckers of the buccal 



230 



