fished, and where the _piranhas_ were most abundant; he stripped, waded out very slowly and cautiously so as not to create a disturbance, and felt about with his toes for the lost article; although the water was over four feet deep and he remained in it fully fifteen minutes, he remained untouched. It is in the dark swamps dotting the chaco like low, glossy islands that the precious quebracho-trees grow. It was also from these same swamps that clouds of ravenous mosquitoes issued with the first signs of failing daylight, and drove us to the refuge of our net-covered hammocks. There we sweltered through the long hours of the night, listening to the angry buzzing of our outwitted assailants, which was not unlike the sound produced by a swarm of enraged bees. I could distinguish a number of different pitches and qualities in the music, blending harmoniously in one general chorus. The varying size of the insects, which ranged from individuals nearly an inch long to the small infection-bearing _Anopheles_, doubtless accounts for the different tones produced by the vibrations of the wings. Brockets were seen occasionally; they left the forest morning and night to feed. In the tall pampas-grass cavies abounded. They came out into the opening beside the railroad just before sunrise and ran about, or sat motionless, when they resembled clods of earth or shadows. Ocelots had worn well-defined paths through the fields in their nightly raids on the cavy community. In the trees we found black howlers, night-monkeys, and giant weasels (_Tayra_); opossums and various species of small rodents held sway on the ground. [Illustration: Fort of Coimbra on the Rio Paraguay.] While there was no scarcity of birds, they were largely species already known to us, and one day one of the men brought in an anaconda ten feet long, that he found basking on the river-bank. After spending a week on the Rio Negro we returned to Asuncion, where we were joined by the commissaries who had just arrived with the equipment. Two days later we boarded the comfortable little steamer _Asuncion_ and started for Corumbá. The four and a half days’ trip up the Paraguay was most interesting, although the heat and insects at times were troublesome. We had entered the great pantanal country, and the vast marshes teemed with bird-life. As the _Asuncion_ fought the strong current and moved slowly onward countless thousands of cormorants and anhingas took wing; lining the pools and dotting the marshes were hordes of wood and scarlet ibises, together with a sprinkling of herons and spoonbills; egrets covered the small clumps of trees as with a mantle of snowy white, and long rows of jabiru storks patrolled both shores. Scarcely a moment passed in which we did not see hundreds of birds. Some of the passengers were armed with rifles and revolvers, with which they kept up more or less of a fusillade on the feathered folk; but fortunately their aim was poor so that little injury was inflicted.