of time of different species of fishes (mainly in fresh water or in naarine 

 display aquaria). We will consider the cases which can be explained by the 

 various reasons later on, but here we must note particularly the necessity 

 of very cautious treatment of the data of MacCallum, who worked in the New 

 York Aquarium and who allowed great inaccuracies to creep into his research. 



Systematic and morphological collections of monogenetic trematodes 

 and research with live animals provided the material for this work. The 

 collections of monogenetic trematodes were conducted either by us directly 

 at the place of location of the live hosts or under laboratory conditions from 

 ichthyological collections chiefly from the Zoological Institute of the Academy 

 of Sciences, U.S.S.R. All in all, the collections contain very significant ma- 

 terial from the most diversified regions of the Soviet Union and foreign coun- 

 tries. One must especially note material from all the South Seas of Russia, 

 from middle Asia (Region Tschu and Tadjikistan and Turkmania and others), 

 from the far East (Amur River System, the Sea of Japan, the Sea of Okhotsk 

 and the Pacific Ocean), from Japan (fresh water and salt water), from the 

 fresh waters of the Maylayan Archipelago, from the United States of America 

 and Canada, and finally from western Europe (Mediterranean Sea, Atlantic 

 Ocean and others). The smallest quantity of material was received from 

 Africa, South America, and Australia. 



The study of live material was conducted by us in the Leningrad 

 region (the Bay of Finland, River Neva and'Ropscha" Fish Farms, small 

 lakes, ponds and brooks) in 1927-1929, 1931-1932, and 1945-1952; on White 

 Lake in 1931; in Karelia (a system of lakes near Konchezero near Peltro- 

 lavodsk) in 1932; on the Volga (near Kostroma and Saratov in the Delta) in 

 1926-27, 1931-32, 1947 and 1953-54; in western Siberia (Barabinskaya 

 Steppe, lakes of the group of Chanov) in 1933; on the Black Sea (Karadag and 

 Sebastopol) in 1927, 1935 and 1947; in the Sea of Azov (in the estuaries of 

 Ahtarinsk) in 1933; the Caspian Sea (on the Island of Sara) in 1931-1932 and 

 1955; in the sea of Aralsk (Aralsk and Muynak and the islands of Uzun-Kair 

 and Kuzdjk-Pes) in 1930; in Tadjikistan (in region of Stalinbad and Vahsha) 

 in 1943-1945; on the Sea of Japan (the Bay of Peter the Great and the western 

 banks of Sakhalin Island) in 1946 and 1949; on the Sea of Okhotsk (Bay of Aniv 

 and the western Shore of Sakhalin) in 1946 and 1949; in the shallow waters of 

 Kurile (in the Island of Shikotan) in 1949; and in the Pacific Ocean in 1955. 



For this work we also utilized the researches on live material P- ° 



which were conducted by colleagues of our laboratory: A. V. Gussew on 

 Hanka Lake, 1948-1949 and in the Barents and Norwegian Seas in 1950; by 

 U. A, Strelkow at the Sebastopol Biological Stations in 1949; and L. F. 

 Nagibina in the Leningrad region in 1946-52; and N. A. Izumova on the 

 Ropscha Fish Farm south of Leningrad in 1951 and 1952. 



XIX 



