286 R. T. GUNTHER. 
Il].—FresH-water Merpvus2. 
The discovery of a new Celenterate living in fresh water 
must always be considered an event of no little importance on 
account of the fewness of such genera. The chief instances 
known at present of fresh-water Coelenterata are the follow- 
ing :— 
Various species of Hydra are almost cosmopolitan. They 
have been described from Egypt (Schmarda), Japan (Hilgen- 
dorf), Australia (Bale, von Lendenfeld), and New Zea- 
land (Coughtrey). The allied genus Microhydra is an 
inhabitant of the New World. 
Cordylophora is known from the fresh and brackish 
waters of England, and of North Germany as far inland as the 
Tegelsee in Prussia; also from America and Australia (v. 
Lendenfeld). 
Polypodium hydriforme, a parasite of the sturgeon, is 
a native of the Volga (Ussow). 
The habitat of Limnocodium is as yet unfortunately un- 
known, but there is but little doubt that tropical America is 
its original home. 
Lastly, in 1890 J. von Kennell (9) discovered Halmo- 
nises lacustris in Trinidad in a fresh-water lagoon com- 
pletely shut off from the sea, and flourishing in the midst of 
such truly fresh-water animals as insect and frog larve, 
Daphnide, Naids, Holosoma, Dero, Clepsine, Planorbis, &c. 
In addition to these truly fresh-water Coelenterates several 
marine forms can tolerate brackish water, for example 
Aurelia aurita from the Baltic, and Crambessa Tagi 
from the mouth of the Tagus, and some others.} 
While treating of such isolated Meduse, it may be as well 
to mention the supposed salt-water Medusa recently drawn 
attention to by Mr. Sclater (13). This Medusa, of which we 
have as yet no details, is an inhabitant of Lake Urumiah in 
Persia. Lake Urumiah has no communication with the sea, 
See also observations by the late Professor Moseley, in his ‘ Naturalist 
on the “Challenger,” ’ 2nd edit., p. 236. 
