The distance from Mazaro, on the Zambesi side, to the Kwakwa at Nterra, is about six miles, over a surprisingly rich dark soil. We passed the night in the long shed, erected at Nterra, on the banks of this river, for the use of travellers, who have often to wait several days for canoes; we tried to sleep, but the mosquitoes and rats were so troublesome as to render sleep impossible. The rats, or rather large mice, closely resembling _Mus pumilio_ (Smith), of this region, are quite facetious, and, having a great deal of fun in them, often laugh heartily. Again and again they woke us up by scampering over our faces, and then bursting into a loud laugh of He! he! he! at having performed the feat. Their sense of the ludicrous appears to be exquisite; they screamed with laughter at the attempts which disturbed and angry human nature made in the dark to bring their ill-timed merriment to a close. Unlike their prudent European cousins, which are said to leave a sinking ship, a party of these took up their quarters in our leaky and sinking vessel. Quiet and invisible by day, they emerged at night, and cut their funny pranks. No sooner were we all asleep, than they made a sudden dash over the lockers and across our faces for the cabin door, where all broke out into a loud He! he! he! he! he! he! showing how keenly they enjoyed the joke. They next went forward with as much delight, and scampered over the men. Every night they went fore and aft, rousing with impartial feet every sleeper, and laughing to scorn the aimless blows, growls, and deadly rushes of outraged humanity. We observed elsewhere a species of large mouse, nearly allied to _Euryotis unisulcatus_ (F. Cuvier), escaping up a rough and not very upright wall, with six young ones firmly attached to the perineum. They were old enough to be well covered with hair, and some were not detached by a blow which disabled the dam. We could not decide whether any involuntary muscles were brought into play in helping the young to adhere. Their weight seemed to require a sort of cataleptic state of the muscles of the jaw, to enable them to hold on.