HirPOPOTAMUS 
203 
It is of course conceivable that the river itself auto¬ 
matically brings down food sufficient to supply a certain 
percentage of its pachydermatous population. Thus 
there is the little water-cabbage (Pistia stratiotes) which 
drifts down in millions from the Sudd regions. One sees 
acres of backwaters and by-channels blocked solid with its 
accumulations, and these stores would yield food for many 
hippos. No more obstructive agent to navigation exists 
than this water-cabbage-—it is largely to its malevolence 
that we owe the Sudd!-—hence, should this hypothesis 
be correct, the antediluvian amphibian is to-day helping 
(albeit unconsciously) to advance modern progress. 
It is notable that even when totally unharassed, the 
hippopotamus deliberately selects the darkness of night 
as his period of activity and all day lies up somnolent. 
By nature, no animal is more inoffensive in disposition ; 
yet persecution modifies that mildness, and to-day many 
hippos have developed characters both savage and 
truculent. Moreover, their vast strength and armoured 
jaws give the power to enforce that truculence. On 
Upper Nile it is of daily occurrence that the dug-out 
canoes of the natives are attacked and scrunched into 
matchwood, some or all of the crew inevitably perishing 
in the melde. Although never myself having experienced 
an actual attack, yet twice when “probing” for a dead 
hippo—(with the view of making fast a rope to his leg 
and so towing him ashore before dark)—the demeanour 
of the rest of the herd became so obviously menacing, 
bellowing and blowing half round our boat, that I 
promptly gave the order to “pull away” and felt no 
small relief when we had regained shallow water. 
A curious metaphysical fact relative to the hippo¬ 
potamus deserves note—that is, that when the animal 
itself is deep under water, yet its snorts and gruntings 
may still be distinctly audible, albeit no air-bubbles or 
other trace appears on the surface. I first noticed this 
phenomenon in East Africa and mentioned it in On 
