26 LÖNNBERG, THE BIOLOGY OF THE CASPIAN SEA. 



Archseobdella esmonti Grimm. 



was found twice, namely at Stat. 9 and 13 in a depth from 9 

 feet to 8 sashen. In the former place it was rather plentiful in 

 the loose mud. In the latter place on Dreyssena bottom only 

 one specimen was found. It is to be observed that Stat. 13 was 

 not far from the estuary of Volga so that the water at that 

 place could not be very salt. Stat. 9 was at the Transcaspian 

 coast off Mangischlak. This remarkable leech thus seems to be 

 distributed över a great part of the North Caspian Sea. 



Specimens of free living Piscicola were found at Stat. 7, 

 12 and 13. At the two former places they lived among algse, 

 at the last the shells offered them suitable places for attaching 

 themselves to while watching for fishes. But as I have often 

 found young specimens of Piscicola in the Baltic attached to 

 stones and algse, it does not seem impossible that these animals 

 should become parasites only when they have come to a more 

 advanced stage after having lived free from the beginning. 



Cordylophora lacustris Allman 



was found several times especially abundant at Stat. 7 among 

 algse. 



From the above given list it is apparent that some of the 

 animals mentioned prefer certain localities which offer them 

 suitable conditions. Neritina and Cardium trigonoides only live 

 on härd bottom not soiled by mud. Many crustacea are exclu- 

 sively, or at least chiefly, found among algse, as for instance, 

 Pseudocuma cercarioides, Gmelina costata and pusilla, Ämathillina 

 affinis^ Gammarus caspiics, varpachovski/i, crassus, abbreviatus, 

 obesus and mceoticus, and Corophiiim robusium. Similar is also 

 the case with Clessinia variabilis. Some other species, again, 

 only live on muddy bottom as Pseudocuma rostrata, Niphargoides 

 caspius and grimmii, Cardiophilus, Coropliium nobile, mzicro- 

 naturn and monodon, larvge of Chironomus, and Amphicteis. But 



