ones which are not homologous to each other. In itself the attaching disc 

 represents, even in the nnost primitive state, an organ of attachment 

 similar to the corresponding developments of the posterior end of certain 

 Rhabdocoela. It is usually equipped with a series of powerfully developed 

 agglutinating glands (see below). However, one must note that in certain 

 groups the attaching disc of the adult monogenetic trematode ceases to ful- 

 fill the functions of attachment, abandoning this function to attaching organs 

 which are placed upon it. 



p. 25 



Fig. 21. Linguadactyla molvae Brinkmann, 

 adult from the gills of Molva dipterygia 

 elongata (Otto) near the shores of Spain 

 (Atlantic Ocean). 



Fig. 22. Polystoma integer- 

 rimum Froelich, adult worm 

 from the urinary bladder of 

 Rana temporaria L. from 

 Peterhof (Leningrad region). 



The most prinnitive is the disc which is weakly delineated from 

 the body, and in actuality represents a direct continuation of the body. 

 Usually such a type of disc is somewhat flattened in comparison with the 

 rest of the body, and in this connection is somewhat more muscular. 

 Examples of such a disc can be seen in Protogyrodactylidae (Fig. 26), and 



16 



