ZOOLOGY. 691 
rate this statement, though it is more strikingly true of the Chilian 
Cordilleras and, as Mr. D. has remarked, is truer of quadrupeds and 
reptiles than of birds and insects. I know of fifty-six species 
occurring on both sides of the Andes of Ecuador, excluding all 
highflying Accipiters and all species ranging north of Panama. 
Mammals, one monkey and one pachyderm; of Birds, one 
thrush, two wrens, one vireo, five tanagers, two antcatchers, 
two flycatchers, five hummers, one trogon, one sawbill and one 
wader; of Reptiles, ten ophidians, two saurians and one batra- 
chian; of Insects, seventeen lepidopters; of Mollusca, three 
Bulimi. . 
The Amazons, the Rio Negro and the Madeira divide the great 
plain into four districts, apparently similar in vegetation, climate, 
ete. Yet these rivers act as barriers to several species, and native 
hunters, understanding the fact, cross the river to procure certain 
animals. Five species of monkeys are confined to the north 
bank of the Amazons, and two to the south side. The blue 
macaw, green jacamar and curl-crested toucan never cross the 
Great River, though butterflies are known to fly-over it. What is 
_ the cause of this isolation? Not the forest, for there is not a 
Single tree which is not found both on the northern and southern 
banks. — Prof. James Orton.* 
_Apsence or Eyes In Cuassreication.— Dr. Hagen’s objection 
to the generic estimation of the lack of visual organs in the cave 
crustaceans is even less weighty than I had supposed ; viz., the 
fact that in certain cave insects, the female sex only is deprived 
of eyes, the males possessing them. No one knows better than Dr. 
agen, that in many genera and even families and higher groups 
of insects the definitive characters are only to be found in the 
sex; and I believe that in some crustaceans it is the female 
Which exhibits the greatest departure from the embryonic starting 
Point. In each case the most extensively developed sex must of 
hecessity furnish the characters which determine the status of the 
Species, But it is unnecessary to refer to special cases of this 
kind, for as I have already shown, the developmental status of the 
= Yes in the blind catfish is very variable in both sexes and opposite 
Sides of the head. This would have been a far better reason for 
- "ejecting the recognition of this character as generic. But on 
* Abstract of a paper read at the American Assoc. Adv. of Sci., 1872. 
