of the larvae takes place later when they already have a developing or 

 already developed 3rd pair of clannps. Also, one can often observe the 

 non-simultaneous development of clamps so that on one side of the disc 



O.M 



Fig. 234. Diplozoon paradoxum Nordnnann, stages of development of the 

 worms from the gills of Abramis brama from the Bay of Finland near 

 Peterhof. Explanation in text. 



there are 3, and on the other, 2 clamps (Fig. 234 C). Finally, we happened 

 to observe the union of larvae which are in different stages of development 

 of the attaching apparatus, i.e., having different ages. The individuals 

 which were united in one or the other fashion gradually grow together ajid 

 at the same time their attaching clamps gradually acquire the final number 

 and sizes. The pigmented eyes disappear during the early stages of 

 development; for the most part this takes place approximately at the 

 appearance of the ventral sucker. 



The development of the sex system and the process of the 

 merging of the larva has not been studied in detail, just as the develop- 

 ment of the excretory system, which is powerfully developed among adult 

 worms, has also not been studied. One must note that certain differences 

 between the data of Zeller and ours (which have not been especially 

 mentioned here) probably are due to the fact that our data relate to D. 

 paradoxum which was collected from the Bream (Abramis brama L. ), 

 whereas the data of Zeller are from parasites of the Minnow (Phoxinus 

 phoxinus L. ). In the materials of A. V. Gussew there are data on D. 

 paradoxum and its development from the Island of Hanka from the gills 

 of Erythoculter mongolicus Basilewsky; basically these data coincide 

 with ours. 



221 



