6 
of known fresh-water forms inhabit it, contracted into thirty- 
nine families or groups, of which fifteen are represented 
in the African, as against twelve in the Indian region. 
Further, the African species, as compared with the Indian, 
are represented in the proportion of two to five, due, it is 
advanced, to the greater uniformity of the physical con- 
dition of the African continent, and to the almost perfect 
continuity of the great river systems, which take their 
origin from the lakes in the centre. 
“This,” says Dr. Giinther, “is best shown by a comparison of 
the fauna of the Upper Nile with that of the West African rivers. 
The number of species known from the Upper Nile amounts to 
fifty-six, and of these not less than twenty-five are absolutely 
identical with West African species. ‘There is an uninterrupted 
continuity of the fish fauna from west to the north-east, and the 
species known to be common to both extremities may be reason- 
ably assumed to inhabit also the great reservoirs of water in the 
centre of the continent. A greater dissimilarity is noticeable 
between the west and north-east fauna on the one hand and that 
of the Zambezi on the other ; the affinity between them is merely 
generic ; and all the fishes hitherto collected in Lake Nyassa have 
proved to be distinct from those of the Nile, and even from those 
of other parts of the system of the Zambezi.” 
“ Africa, unlike India, does not possess either alpine ranges 
or outlying archipelagoes, the fresh waters of which would swell 
the number of its indigenous species; but at a future time, when 
its fauna is better known than at present, it is possible that the 
great difference in the number of species between this and the 
Indian regions may be somewhat lessened.” 
To give a more extended but brief comparison of the 
fresh-water fauna of the African, as against the other 
regions, I would quote that: 
“The regions with which Africa (like India) has least similarity 
are, again, the North American and Antarctic. Its affinity with 
the Europo-Asiatic region consists only in having received, like 
