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president’s address. 
water lagoon on the cost of Trinidad. 
Thaumantias maeotica. In the Sea of Azov, and also in the 
Bay of Naples. (Mayer, 1910.) 
Moeotias inexspectata occurs in the Sea of Azov, and also in 
the estuaries of the Don and Kuban Rivers. 
Polypodium hvdriforme is a Hydroid found parasitic on 
sturgeons’ eggs in the Caspian Sea, and has a free- 
swimming stage. 
In addition to these species may be mentioned the large 
Jellyfish, Crambessa, which is found in the estuaries of 
large rivers from France to Senegambia, and also in East 
Africa, but which does not actually reach fresh water. 
Among the Crustacea representatives of almost every order 
are found in fresh w r ater, but nearly all of them are powerful 
swimmers, or creep on the bottom, or are parasitic on fish. 
Very few are small species at the mercy of currents. The 
majority of the Copepoda are ancient inhabitants of fresh 
water, but there are a few free-swimming species which are 
probably recent immigrants. Such are Limnocalanus and 
Poppella. Limnocalanus grimaldii is found in the Baltic, in 
the Caspian Sea and in the Arctic Ocean, and there are two 
other species found only in fresh w T ater in Europe, North Asia 
and North America. Poppella guernei lives in either fresh or 
rather brackish water in the South of France, Tunisia, Italy 
(Lake Avernus), and in the Caspian Sea and its neighbourhood. 
In addition to these Calanoids, representatives of the Cyclopid 
genera Oithona and Limnoithona occur in fresh water in China 
and South America. Oithona is, in fact, a genus capable of 
living in widely different degrees of salinity. 
The classical example among Crustacea is, however, Mysis 
relicta. It is a species so closely related to M. oculata as to 
be regarded by some as a variety of the latter. But, while 
M. oculata is a marine form widely distributed round the 
Arctic coasts of Europe and North America, though not found 
in the Baltic, M. relicta is an exclusively fresh water species 
found in various lakes of Europe and North America. Its 
distribution is as follows : — 
