808 THE AMERICAN NATURALIST. 
known is found in a West Indian fish, the vaca, which bears 
the incongruous name of Hypoplectrus unicolor. In the typical 
vaca the body is orange with black marks and blue lines, the 
fins checkered with orange and blue. In a second form the 
body is violet, barred with black, the head with blue spots and 
bands. In another form the blue on the head is wanting. In 
still another the body is yellow and black, with blue on the 
head only. In others the fins are plain orange, without checks, 
and the body yellow, with or without blue stripes and spots, and 
sometimes with spots of black or violet. In still others the 
body may be pink or brown, or violet black, the fins all yellow, 
part black orallblack. Finally, there are forms deep indigo blue 
in color everywhere, with cross bands of indigo black, and these 
again may have bars of deeper blue on the head or may lack 
these altogether. I find no difference aniong these fishes 
except in color, and no way of accounting for the differences 
in this regard. 
A species of puffer (Tetradon setosus) shows similar remark- 
able variations, being dark gray with white spots, but varying 
to indigo blue, lemon yellow, or sometimes having coarse 
blotches of either. Lemon-yellow varieties of several species 
are known, and these may be due to a failure of pigment, a 
sort of semi-albinism. True albinos, individuals wholly with- 
out pigment, are rare among fishes. 
