development of the attached larva apparently proceeds in the usual way 

 (unfortunately this has not been fully studied). It is known only that one 

 hook of the first pair of middle hooks does not grow at all in the post- 

 embryonic period. During the early stages of development this hook 

 (during the observation on live worms) acts completely normally and 

 serves, just as the one corresponding to it, for the attachment of the 

 larva^ whereas among adult individuals it doesn't play any role whatsoever. 



0.01mm 



9. The development of Diplectanum Diesing 



As is known, the genus Diplectanum (Fig. 14) is characterized 

 by the presence of a more complex attaching arnaature than among all the 

 previous genera. The attaching apparatus (Fig. 56) consists of 14 lateral 



hooks, 2 pairs of middle 

 hooks, 3 connecting plates -- 

 one unpaired middle and 

 2 paired, articulated with 

 the middle hooks, and 

 finally of 2 peculiar supple- 

 mentary discs, all deployed 

 on the disc. These discs 

 (whence comes the name of 

 the genus) lie on the upper 

 edge of the attaching disc 

 one on the ventral and one 

 on the dorsal side and are 

 equipped with a large 

 number of small chitinous 

 stick-shaped fornnations 

 with hook-shaped offshoots 

 located in regular rows 

 (Fig. 181). The develop- 

 ment of the genus unfor- 

 tunately has not been studied; 

 known are only the free- 

 swimming larvae of D, 

 aculeatum Parona and 



Fig. 181. Diplectantim aculeatum Parona 

 and Perugia, chitinous armature "plectans" 

 of an adult worms from the gills of Corvina 

 nigra Cuv. and Val. from the region of 

 Karadaga (Black Sea). On the left is one 

 row, greatly magnified. 



Perugia and D. similis Bychowsky, a new species which is very close to 

 the first species ajad of which we collected a large number of individuals 

 in June 1935 at the Sebastopol Biological Station and in July -August 1949 

 at the Karadaga Biological Station from the eggs deposited by worms on 

 the Gorbil ( Corvina nigra Cuv. and Val.) (Humpback Salmon, nobis) . 

 These larvae resemble those of the genus Dactylogyrus but deserve 

 detailed description. The free -swimming larvae (Fig. 182) which have 

 just emerged frona the egg have an elongated, torpedo-shaped form with 

 blunt anterior ends and a very sharpened posterior end. At the anterior 



166 



178 



