PRESIDENT’S ADDRESS. 
475 
Marine Animals in Fresh Water. 
Having now discussed the difficulties which have to be sur- 
mounted by marine animals entering fresh water, we must pass 
on to a consideration of the animals which we regard as com- 
paratively new immigrants, and the means by which it may be 
supposed that they have established themselves. It is outside 
the scope of this paper to give any extensive list of marine 
species in fresh water, but it will suffice to deal with a few 
selected examples. 
Perhaps the most striking examples are the Medusae of fresh 
water. The Medusae are feeble swimmers and peculiarly sus- 
ceptible to changes of temperature and salinity ; so much so 
that they may almost be taken as “ Current indicators.” 1 Yet 
several species are now known which are found in inland waters 
in various parts of the world, and which may be mentioned in 
detail. 
Craspedacusta (Limnocodium) sowerbyi is known only from 
tanks in some European Botanical Gardens. 
Craspedacusta kawai is found in the Yangtse-Kiang, 1,000 
miles from its mouth. 
Microhydra ryderi is a small Hydroid found in the Delaware 
River, near Philadelphia, which buds off a Medusa, 
apparently allied to Craspedacusta. 
Limnocnida tanganyicae is found in Lake Tanganyika, and 
also in Victoria Nyanza, and in the Niger River. 
Limnocnida indica. This Medusa occurs in Western India, 
in tributaries of the Krishna river, and in a lake at 
Purulia (Chota Nagpur), and differs little from the pre- 
ceding species. 
Moerisia lyonsi. Found, together with the Hydroid from 
which the Medusa is budded, in the Birket el Kurun, in 
Egypt, by Boulenger and Cunnington. Boulenger 
believes that the Medusa of the Caspian Sea (Caspio- 
nema pallasi) is identical with that of the Fayyum. 
Thaumantias lacustris. Found by Von Kennel in a fresh 
1. A. Walter, Deutsch. Geog. Bla tter, Bremen, 5,1890. 
