most part with only one pipe, more seldonn it is complex, with a 

 supporting apparatus. 



Parasites of Perciformes, predominantly of marine, less 

 often fresh water Percoidae. 



This family is separated by us and combines the repre- 

 sentatives of two known subfamilies --Diplectaninae and Ramnocercinae 

 which were ascribed to Dactylogyridae until the present time. Important 

 characters which arise anew in the process of evolution and which bear an 

 obviously progressive nature serve as a basis for the establislment 

 of the new family. Such characteristics , in the first place, are the 



special attaching formations which appear independently of the usual 

 chitinous armature. These new attaching organs- -secondary discs or 

 their derivatives have an important adaptive significance which allows 

 the worms to attach themselves between the gill filaments of the host 

 much more strongly. There is no doubt whatsoever that Diplectanidae 

 originate from Dactylogyridae; however, they are considerably 

 separated from the latter. We can consider that, within the limits of 

 Diplectanidae, the evolutionary development proceeds in the direction 

 of increasingly narrowed adaptability, not only to the host but also to 

 specific sections of the gills of the latter. Thus, the paired species of 

 Diplectanum from Corvina nigra Salv. (D. aculeatum Parona and 

 Perugia, and D. similis Bychowsky) studied by us and also the paired 

 species of Lamellodiscus from Sargus annularis (L. ) (L^ elegans 

 Bychowsky and L. fraternus Bychowsky) are characterized by their 

 location on different sections of the gills and, even more specifically, 

 of the gill filaments and this location is also reflected in the morpho- 

 logical peculiarities of the worms. The attaching apparatus of D^ 

 similis and L. fraternus living at the bases of the gill filaments has 

 more elongated connecting plates, in connection with which their 

 attaching disc is also elongated in the lateral direction and its size 

 more or less corresponds to the width of the gill filaments of the host. 

 Hence, the increasingly narrowed adaptability to specific places of 

 habitat (to the microhabitat, nobis ) leads to the appearance of supple- 

 mentary adaptations for the fixation of the animal on the place which 

 is attained by the development of new formations - -secondary discs or a 

 system of spear-shaped thorns. It seems to us that it is possible to 

 connect the origin of the secondary discs and the spear-shaped thorns 

 with the cuticular "little scales" possessed by certain Dactylogyridae 

 and which are widely distributed annong Diplectanidae (see page 43 ), 

 the alteration of which apparently gave rise to the specialized chitinous 

 parts of the secondary discs. As regards the spear-shaped thorns^ 

 there is no doubt that they are homologous to the armature of the 

 secondary discs. Thus, during the comparison between the structure 



422 



356 



