412 REPORT—1905. 
Secrion D.—ZOOLOGY. 
PreEsIDENT OF THE SEcTION—G. A. BouLencEr, F.R.S. 
CAPE TOWN. 
WEDNESDAY, AUGUST 16. 
The President delivered the following Address : 
The Distribution of African Fresh-water Fishes. 
I rutnk I may ascribe the honour of having been chosen to preside over this 
Section to the fact that I have specially applied myself to the study of a large 
class of the animals of the part of the world in which we are for the first time 
assembled. The subject of the Address which it is the custom to deliver on 
such an occasion was therefore not difficult to choose—a general survey of the 
African fresh-water fishes from the point of view of their distribution. 
It has repeatedly been pointed out that no division of the world can answer 
for all groups of animals, differences due to the period at which they appeared 
and to their ability or inability to spread over obstacles, whether of land or 
water, precluding any attempt to make their present distribution fit into the 
frames of the general zoo-geographer. The great divisions of the earth, as out- 
lined by our eminent Vice-President, Dr. Sclater, nearly half a century ago, and 
based mainly on a study of passerine birds, have therefore varied considerably 
according to the standpoint of the many workers who have followed in his foot- 
steps. Fresh-water bony fishes particularly lend themselves to a uniform treat- 
ment, their principal groups having sprung up, so far as paleontological data 
teach us, about the same period in the history of the earth, and branched off in 
many directions within a, geologically speaking, brief lapse of time, most of 
them, besides, being regulated in their distribution by the water-systems. How 
greatly their distribution differs from that of terrestrial animals has long ago 
been emphasised. Thus, latitudinal range, so striking in many African reptiles, 
does not exist in fishes: the key to their mode of dispersal is, with few exceptions, 
to be found in the hydrography of the continent; and, as first shown by 
Dr. Sauvage, latitude and climate, excepting of course very great altitudes, are 
inconsiderable factors, the fish-fauna of a country deriving its character from 
the head waters of the river-system which flows through it. In this way, for 
instance, the Lower Nile is inhabited by fishes bearing a close resemblance to, 
or even specifically identical with, those of Tropical Africa, and strikingly con- 
trasting in character with the land-fauna on its banks. Such being the case, it 
seems at first as if the geographical divisions of the fish-fauna were a matter 
