other ways less adapted to succeed in the
environmental complex. The same statement can be made of all the many,
many other known factors in development, from fecundity to concealing
coloration; and behind them lie forces as to which we veil our
ignorance by the use of high-sounding nomenclature--as when we use
such a convenient but far from satisfactory term as orthogenesis.

II. UP THE PARAGUAY

On the afternoon of December 9 we left the attractive and picturesque
city of Asuncion to ascend the Paraguay. With generous courtesy the
Paraguayan Government had put at my disposal the gunboat-yacht of the
President himself, a most comfortable river steamer, and so the
opening days of our trip were pleasant in every way. The food was
good, our quarters were clean, we slept well, below or on deck,
usually without our mosquito-nettings, and in daytime the deck was
pleasant under the awnings. It was hot, of course, but we were dressed
suitably in our exploring and hunting clothes and did not mind the
heat. The river was low, for there had been dry weather for some weeks
--judging from the vague and contradictory information I received
there is much elasticity to the terms wet season and dry season at
this part of the Paraguay. Under the brilliant sky we steamed steadily
up the mighty river; the sunset was glorious as we leaned on the port
railing; and after nightfall the moon, nearly full and hanging high in
the heavens, turned the water to shimmering radiance. On the mud-flats
and sandbars, and among the green rushes of the bays and inlets, were
stately water-fowl; crimson flamingoes and rosy spoonbills, dark-
colored ibis and white storks with black wings. Darters, with
snakelike necks and pointed bills, perched in the trees on the brink
of the river. Snowy egrets flapped across the marshes. Caymans were
common, and differed from the crocodiles we had seen in Africa in two
points: they were not alarmed by the report of a rifle when fired at,
and they lay with the head raised instead of stretched along the sand.

For three days, as we steamed northward toward the Tropic of
Capricorn, and then passed it, we were within the Republic of
Paraguay. On our right, to the east, there was a fairly well-settled
country, where bananas and oranges were cultivated and other crops of
hot countries raised. On the banks we passed an occasional small town,
or saw a ranch-house close to the river's brink, or stop