countered, or more precisely, are encountered very rarely outside of 

 their connections with the chitinous organs. As a result of this, it is 

 nnore convenient to group the attaching organs as a whole, that is by the 

 combination of separate parts, which form an independently functioning 

 unit. Systematizing in accordance with this principle we obtain four 

 basic groups, specifically: a group of hook-shaped organs, a group of 

 supplementary discs with chitinous armature, a group of suckers, and 

 a group of attaching valves. Let us immediately note that the same 

 species of animal can have attaching organs of one, two, or three types. 



p. 28 



Fig. 29. Tetraonchoides paradoxus Bychowsky, 

 adult worm from the gills of Uranoscopus 

 scaber L. from the Bay of Sebastopol (Black 

 Sea). 



Fig. 30. Thaumatocotyle 

 dasybatis (MacCallum), 

 adult worm. (According 

 to Price, 1938). 



The first group, that is the hook-shaped organs, is the most 

 widespread. It is represented by chitinous structures of a very different 

 shape and size and by different chitinous parts which connect or support 

 the hooks, and also the attaching disc itself. Chitinous hooks are sub- 

 divided into the edge type and central type. 



20 



