VOYAGE UP THE COAST TO PARA'. 143 
creek, having first fastened the seine across from shore 
to shore at a lower point, and when they have gained 
a certain distance above it, they spring into the water 
with a great plash and rush down the creek in a line, 
driving the fish before them into the net. One draught 
alone filled the boat half full of fish. Mr. Agassiz was 
especially interested in seeing alive for the first time the 
curious fish called " Tralhote" by the Indians, and known 
to naturalists as the Anableps tetrophthalmus. This name, 
signifying " four-eyed," is derived from the singular struc- 
ture of the eye. A membranous fold enclosing the bulb of 
the eye stretches across the pupil, dividing the visual 
apparatus into an upper and lower half. No doubt this 
formation is intended to suit the peculiar habits of the 
Anableps. These fishes -gather in shoals on the surface 
of the water, their heads resting partly above, partly below 
the surface, and they move by a leaping motion somewhat 
like that of frogs on land. Thus, half in air, half in water, 
they require eyes adapted for seeing in both elements, and 
the arrangement described above just meets this want. 
August 19/7L To-night at ten o'clock we go on board 
the steamer, and before dawn shall be on our way up 
the river. This has been a delicious week of rest and 
refreshment to me. The quiet country life, with morning 
walks in the fresh, fragrant lanes and roads immediately 
about us, has been very soothing after four months of 
travel or of noisy hotel life. The other day as we were 
going into town we found in the wet grass by the road- 
side one of the most beautiful mushrooms I have ever 
seen. The stem was pure white, three or four inches in 
height, and about half an inch in diameter, surmounted by 
a club-shaped head, brown in color, with a blunt point. 
