Vol. XI, Nos. 10 & 11.) The Fauna of the Jordan System. 465 
N.S.] 
brackish water, is not known to enter the sea; yet it has been 
proved in the Madras Aquarium! that it will live for years 
in pure sea-water. Dr. Henderson tells me, moreover, that the 
individuals in that aquarium, though living under unnatural 
conditions, are not affected by a bacterial and fungoid epidemic 
disease that periodically destroys large numbers of marine fish 
in adjacent tanks. The fact that the genus has penetrated so 
far east as India is, indeed, in itself evidence of the adapta- 
bility of the Cichlidae. 
It is thus clear why African fish have been able to survive 
in the Jordan and its lakes—because the species are so adaptable 
in their habits and physiology that they can survive changes 
sufficiently violent to kill the majority of aquatic animals. 
That several of the Jordan species of Cichlidae are 
in many widely distributed and adaptable animals, isolated 
groups of individuals are liable to become so differentiated that 
they ultimately form distinct species. © 
To turn to the invertebrates; a small number of species 
that are common to Africa and tropical Asia, and may, so far as 
their structure and distribution are concerned, have had either 
an Ethiopian or an Oriental origin, are found in the Lake of 
Tiberias; but there is not a single invertebrate known from any 
part of the Jordan system that can be confidently claimed 
as Ethiopian even in respect to genus. 1 have already drawn 
attention (p. 460 andea) to the absence of exclusively Ethiopian 
forms, in particular amoug the Unionidae. 
Of the Palaeotropical species all are either extremely 
adaptable in their habits or else may be classed rather as 
amphibious than as aquatic. To the former category belongs 
the mollusc Melania tuberculata, a species found practically 
everywhere in both the Ethiopian and Oriental Regions and 
also in some Mediterranean localities. It is one of the com- 
monest of the Indian freshwater Gastropods and is found in 
this country both in fresh and in brackish water, being pecu- 
1 Henderson, Guide to the Marine Aq 
2 In Preston’s recently published volume on 
itis. 
the Fauna h India (1915, pp. 15-17) seven Indian varieties 
of “Tiara (Striatella) tuberculata”’ are described. It is : wie er ae 
nate t o serious attempt seems to hav n made os ec vam - 
which might have been of the greatest possible value ; 
the sisartnhinel aictiieaiae of the Indian Mollusca. to collate even the 
recorded localities of the Gastropods described. 
